All bitcoins receive as a reward the one who generated the next block. The reward received for the blocks can be used after receiving 120 confirmations (that is, the network allows you to spend the reward in about 20 hours).
Does this mean that the bitcoin that was mined needs to be withdrawn within 20 hours?
No. This means that he entered the wallet after 20 hours.
And how is it charged? Just programmed into your wallet?
There are 3 main types of accrual of awards:
Proportional - After a pool finds a block, the reward is divided in proportion to the contribution of each participant.
PPS - Each standard option sent is rewarded (from the calculation of the current block reward divided by the current difficulty).
Score - An evaluation system for rewarding standard options, the algorithm of which is determined by the pool organizer.