Your first stop with questions like these should be vim’s internal help, :h f and :h t. However, in this case, those entries are a bit cryptic without an example. Suppose we had this line (^ = cursor position):
The quick brown fox jumps over the lazy dog.
^
These commands find characters on a line. So fb would place the cursor here:
The quick brown fox jumps over the lazy dog.
^
t is like f but places the cursor on the preceding character. So tb would give you:
The quick brown fox jumps over the lazy dog.
^
You can remember these commands as find and till. Also, you can prepend the commands with a number to move to the nth occurrence of that character. For example, 3fb would move to the third b to the right of the cursor. My example sentence only has one b though, so the cursor wouldn’t move at all.