This is the process of aggregating several cheap shares into one more expensive one of the same company, as a result of which the total value does not change.
Example: On 30.04, you had 1000 AMD shares at a price of $1 per share, i.e., the value per $1000, the company announced that from 01.05, a 1 for 20 stock split will take place.
This means that on 1 May, at the opening of the market, you'll only have 50 (1000/20) AMD shares at a price of $20 per share. In this case, the total cost will remain the same at $1000.
*If receiving fractional shares, the client receives the cash equivalent of these shares.