? = Previous item is match 0 or 1 times.
* = Previous item is matched 0 or more times.
+ = Previous item is matched 1 or more times.
{n} = Previous item is matched exactly n times.
{n,} = Previous item is matched at least n times.
{n,m} = Previous item is matched at least n and at most m times.
? (after any of above) = Match as few as possible times.