Mining Cryptocurrency mean that you are offering your computing powers (hashing power) to the network whether it is from your Central Processing Unit (CPU), Graphic Processing Unit (GPU) or Application Specific Integrate Circuit (ASIC).
So let assume that you already know some coins or token in Cryptocurrencies list like Bitcoin, Litcoin, Ethereum and so on. Currently there are 3 tpye of algorithm use in Cryptocurrency including Proof of Work (POW), Proof of Stake (POS) and Hybrid. Keep in mind that only Proof of Work coin are mineable.
To start mining you need hardware. GPU and ASIC are both profitable to mine. Since both of them consume electric city to run so you need to pay electric bill every month.
1. GPU Mining
Most of altcoins this day are GPU mineable such as Ethereum, Zcash, Monero and the list goes on. There are two type of GPU miner including Commercial and Hobby miners. Commercial miner usually mine with lots of GPU at the same time, hobby miner refer to those people who have high performance computer especially gamer, just let it run when you don't use your computer.
2. ASIC Mining
ASIC mining hardware were made specifically for one coin. It gave more hashing power than GPU so it is more profitable for one particular coin. Bitcoin, Litcoin and Dash are those coin which more profitable to mine with ASIC rather than GPU due to the super high difficulty.
Overall no matter which hardware you use to mine, it benefits as a whole. It mean you help scale decentralize network and you make profit at the same time. But the downside is those hardware consume a ton of electric power.