Check whether a cell contains a substring

Question

Is there an in-built function to check if a cell contains a given character/substring?

It would mean you can apply textual functions like Left/R

Answer 1

This formula seems more intuitive to me:

=SUBSTITUTE(A1,"SomeText","") <> A1

this returns TRUE if "SomeText" is contained within A1.

The IsNumber/Search and IsError/Find formulas mentioned in the other answers certainly do work, but I always find myself needing to look at the help or experimenting in Excel too often with those ones.