Hello amazing steemians, 
Generally new users and investors come aboard as the steem platform grows. Each and every new member has his/her reason why they want to be a part of the blockchain. Probably to earn some coins, invest in steem or steem power, go through motivational or life contents. Best know to them. But one thing is certain, not everyone is getting the same piece of pie.
Probably some users will go through a post/content and after reading, the upvote the post and thereby leaving that particular content with some $. In some cases, the upvote might be huge (only a whale can do that) or less, probably cent (minnows). All the same, the vote weights depends on the amount of steem power the voter has. They have the ability to adjust the voting percent or sometimes they might just give it a 100%. In real life when a whale moves, probably everything and all the fishes in the sea feels his presence. So is it when ever we are kissed by a whale, there is the UN-explainable excitement we derive.
Minnows, Dolphins, and Whales exist in every financial market. If whales make a big sell order, they can crash entire markets with small caps- and if they buy, everyone makes money.
- Minnows
This is an ordinary user on steemit. Peradventure they just joined the platform for the first time, maybe someone told them about it, and are looking all desperate.
When it comes to vote, minnows have very little capability to influence their vote on another user, as a result of low steem power. It's impossible for minnows with low s.p (steem power) to give a tip in terms of upvote on an article. The best they can offer is $0.1, and then with time they increase in steem power.
All the same, they still have a good role to play here, from my research minnows are mostly the ones who promote steemit, invite their friends and neighbours to come aboard on the platform. With that, they make the platform attractive to others thereby making steemit know in some areas where no one knows it.
Tip: if you're a whale and you notice any steemian trying to bring some positive value to the block chain, it is advisable to support and encourage them. One day they will be a whale to. ;)
- Dolphins
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Dolphins on the other hand has their own part to play. They are also investors but with little decent amount of money. Generally, they've invested a few thousands on steem power. Their upvote approximately gives you some decent cents on a single vote. One good thing about a dolphin's upvote is that, as they vote they attract others to vote on the particular post. Through investment and other money earned from posting and up-voting contents, the steem power in their wallets grows by itself just by sitting there. With time they get powerful and influential on the blockchain. Try as much as you can to keep positive relationship with a dolphin, they are likely to become a whale overnight.
- Whales
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This are the big boys and girls present here on the blockchain. The big kahunas!!! When ever they like something, you'll definitely know. Most times, they are always the one's whose post are on the trend section, with quite a good number of monetarily valued digits under them. These whales are popping over 50,000 - 1,000,000 steem power or more. Whenever they upvote your content there is a feel good record ignited in your brain. Without them this entire block chain will be nothing but a joke. They play a very crucial part on the steem block chain, especially when it comes to $. In fact they deserve all the accolades.
Thanks for reading my post