Substring

A substring of a string $T=t_{1}t_{2}\dots t_{n}$ is a string $P=p_{1}p_{2}\dots p_{m}$ such that $t_{1+i}\dots t_{m+i}=p_{1}\dots p_{m}$.

T = BANANA
     |||
P =  ANA

Given a pattern P, you can find its occurrences in a string T with a String searching algorithm.