What are the numbers at the bottom of the check used for? These are the transaction numbers.
These are the check numbers.
These are identification numbers used to identify the bank, your account number, and the check number.
These are the numbers that tell the bank how much is currently in your account.

These are identification numbers used to identify the bank, your account number, and the check number.

Explanation:

Every check has a set of three numbers at the bottom. The routing number, account number, and check number.

The routing number is at the bottom left corner. It a nine-digit code used to identify the financial institution associated with the check.  Each and every financial institution has a unique routing number.

The account number is in the middle of the three numbers. The account number is private and unique to every customer.

The check number is the last one and is a four-digit number. It identifies a check drawn by a particular customer.

Therefore, the numbers on a check are for identification and tracking purposes.