Symbol Description
* Match 0 or more of the previous
+ At least one of the previous
? Optional - matches 0 or 1 of the previous
{n} Exact count e.g. {5} matches 5 occurenes.
{n, m} Match a range of counts. e.g. {5, 10} matches everything between 5 and 10 occurrences.

e.g.

.*
.+
\d{10}
(a|b)?

e.g. match number of 1 or 2 digits. Using either pattern.

\d?\d
\d{1,2}

e.g. JS comments over 80 characters long

// .{80}

Note there may be text before or after the match - this is not restricted like using ^ and $.