What is the name of the substring search algorithm (class of algorithms?) that uses a character probability map?

Question

Algorithms

As far as I remember, the essence is something like this: for a pattern of n-characters, each (i * n) character of the string is checked in a row. If the character of the string is contained in the pattern at a certain position, the count of other characters of the pattern starts from it in the reverse order of the probability of finding the character in the string. The characters are checked until the first mismatch, if all matched, then the substring was found.

Once upon a time I heard about him at the institute, but now I can’t google it.