Brute force method is common in cryptography, computer science: it means to check ALL possible cases.

For example: I give you two prime numbers. To make it simple let's take 11 and 13.

Multiply it you have 143.

What if I ask you what two prime numbers build up 143? You cannot find solution unless you check all possible cases.

In cryptography, the higher the number, the more time it takes to find the solution. RSA encryption uses this and people have not found a way to decrypt it except brute force