Searching is done with:
/hello/
Find first line in of after current line.
Just // will repeat the search.

Theere are special characters that can be used in the pattern:
.	Match any character.
x*	Match any numbers of x (0 or more).
[abc]	Match 'a', 'b' or 'c'.
[0-9]	Match any digit 0 - 9.
[a-z]	Match any lowercase letter.
\x	Match 'x' where 'x' can be any character except '(' and ')'.

Example:
s/ab.d/ABCD/
Substitute any string 'abcXd' against 'ABCD' where X can be any character.