How can you not know this? You joined Bitcointalk in 2014, you're mining Bitcoin and thus earning from block rewards and transaction fees, but you don't know what transaction fees are? You're an early adopter and miner, how did this happen?
People don't need to understand the concept of BTC to be able to mine it.
There are tons of simple tutorials on how to setup a miner and connect it to a mining pool.
A lot of people invest in BTC without knowing how to store them properly.
People have shown us (multiple times) that you don't need to understand what you are doing. If it works, it works for them.