"Long position" - it's when you buy something - some stock - thinking that it's a cool stuff, and it's going to grow in value, like, it can be some shares in a company that produces robots that are going to rule the planet a decade later or something. In other words, buying something that you think is worth buying and holding.
"Short position" - it's when you think that something apparently sucks, like there's a company that produces photographic film, and it's kinda obvious that photographic film is obsolete, and it's like, you know that a month later nobody is going to buy this shit anymore because of DSLR and stuff. So you just borrow the shares of that loser company and go to the market and say like "Yeah, here's this cool stuff," and sell those shares. You got to pay the dividends to folks who bought those shares until the company goes bust, and you buy those shares back for pennies from the panicking and sweaty muppets, who made this brilliant decision to invest in the photographic film industry. Then you return this shit to the photographic film company, count your profits, and wave all the losers goodbye.
"Margin trading" - trading with the borrowed money. Like, with my own money I can buy one apple then sell it elsewhere and make one dollar profit on the price difference. Or I can borrow a million dollars and make like, a million dollar profit in a blink of an eye. The downside is that if something goes wrong, like, prices decline or something, I'm going to get properly fucked real quick.
"Margin call" - a call from a guy - the one, who lent me money and holds whatever investments I made as a collateral for my debt - in which he informs me that I'm fucked. Or, to make it sound less dramatic, that I need to deposit additional cash on my account asap, or my position will be liquidated, after which I'll still be owing him a huge pile of money.
"Low liquidity" - this is when, for example, I invested all my money in the shares of a company that produces, for example, smart robots that are going to take over the Earth, and all that. So I know that those shares are going to grow to the moon, the sky is the limit, and I'm going to become a multi-billionaire in the nearest future. Like, maybe in half of a year. And then, suddenly, I'm hungry and need to buy some bread. And ok, I don't have any money, only those smart robot shares, so I think like, "Probably I can sell some, get cash, and buy bread." And I go to the market, but the folks there say like, "We don't know, what the fuck is that. Why you ask such a high price for this shit?" So I need to sit and wait for half a year without bread until I get rich. At the same time, I realize that in half a year I will simply die from starvation. So I sell all the shares for pennies, collect change, buy a loaf of bread, and think about my further options of making money as a pauper. I don't have any valuable stock anymore, nor do I have money. If I was smart I would've left some cash for urgent expenses - bread, electricity bills, etc. - while buying those robot shares, but I haven't. As a result, I got broke instead of getting obscenely rich. All it took was a few dollars in cash that made a crucial difference. This is the essence of "liquidity crisis"
"Liquidity Crisis" - it's when you need to buy bread, but you don't have money. Instead, you have some stock, highly profitable in the future - investments in AI, self-driving cars, smart robots - that you cannot sell right now. In other words, you are fucked.
"Futures" - it's when I grow, say, weed. I don't know what market price for weed is going to be when it's ripe and ready to be rolled in joints. I wonder, like, "What if it will be legalized, and every muppet will grow weed in flower pots on their windowsills? Then it'll cost like, next to nothing, and all the money I spent furnishing a clandestine weed lab in my basement will go down the drain." So I catch some guy, and say, like, "Hey, here's this limited edition of weed that's going to be ready in three months, and you can secure the purchase right now for a very attractive price!" The guy cannot resist the temptation, and we strike a bargain, according to which he buys that weed three months later for, like, $5 per gram. Cuz it's really cool and potent, and I need to cover my expenses on that underground lab of mine, and all that. Then three month later, there's a massive drought, hurricane, and apocalypse. Cops roll up everybody, and the weed costs like, $100,000 per gram. Meanwhile, that guy comes to me, shoves into my face that futures contract we signed three months before, and demands weed for $5 per gram. Then I realize that it hasn't worked out the way I planned.
"Call option" - It's like, for example, I have some piece of antique furniture, say, a wardrobe that was preserved from the times of Ancient Rome. Like, back then, it was used by Caligula himself to do whatever he did back then. So yes, I guess it may have some value, and its value can grow during the following year, or it can decline. I don't know for sure because I don't know shit about the antique market. What I know for sure is that I need a hundred bucks right now, to pay my bills, buy bread, and all that. So what I figure is that I don't really want to sell this wardrobe because of memories and stuff. And, at the same time, I suspect that in the nearest future the market of Ancient wardrobes used by Caligula is going to decline - the wardrobes are going to get cheaper. So I call my friend and say, like, "Look, I know you like antiques and stuff, so here I have an awesome offer for you! I have this antique wardrobe used by Caligula in Ancient Rome. Would you like to buy it from me for, say, $100,000? Oh, you don't have enough cash right now? It's not a problem, really. I'll give you an option to buy this wardrobe whenever you want in the course of the next three months for this price. And, you know what? It's an especially good deal for you cuz, for all I know, the market of Caligula's wardrobes is going to grow, so that stuff is going to be much more expensive real soon, like, it'll cost $200,000 or $1,000,000, I don't know. So, in fact, I'm doing you a favor. Would you mind giving me a hundred bucks right now, like, for my generous offer, and for how nice of a person I am, in fact, and all that" So, in the end, I pocket a hundred bucks, and, as I predicted, the market of Caligula's wardrobes goes south, wardrobes cost next to nothing, my friend never calls me again, and I don't need to sell my precious piece of furniture. Win!