10: The Bitcoin system is designed so that, on average, a new block is mined every 10 minutes.
50: The initial block reward at genesis(2009) was set to 50 bitcoins. This is the reward a miner gets for solving a new block. Every roughly 4 years this number is halved.
2016: The mining difficulty is adjusted every 2016 blocks to keep blocks 10 minutes apart on average. If the miners are too fast, the difficulty increases, and if they're too slow, it becomes lower. This number comes from choosing roughly 2 weeks as the amount of time between difficulty adjustments. 2016 = (60 * 24 * 7 * 2 / 10).
2140: The approximate year in which the last reward will be given to a miner, assuming the precision hasn't changed by that time. If the precision is increased, then mining rewards will continue as usual with their halving mechanism, always getting closer and closer to the maximum of 21 million bitcoins.
210,000: The mining reward is halved after this many blocks have been mined. It's roughly 4 years assuming constant 10 minutes blocks (60 * 24 * 365 * 4 / 10 = 210,240)
21,000,000: This is the maximum amount of bitcoins ever to exist(Note that for some technical reasons there will be a few less sats than that though). You can get to this number by doing a bit of math:
Each rewards era has half of the reward as before: 50, 25, 12.5, 6.25, 3.125, 1.5625, etc. If you sum them all up you get an infinite geometric series that can be solved and the result is 100:
Each one of the 210,000 blocks of each era receive their corresponding rewards, so you can sum them all up to get the total number of bitcoins: 210,000 * 50 + 210,000 * 25, etc, which is the same as doing 210,000 * (50 + 25 + ... ), and we already know the number in parenthesis is 100. So total rewards are 210,000 * 100 = 21,000,000.
100,000,000: The amount of satoshis in one bitcoin. Satoshis are also called sats.
