Quantifiers are used to specify the number of occurrences to match against. There are very useful in declaring patterns in real life applications. Lets explore this:

X{n} – means exactly n occurrences of X.
X{n,} – means at least n occurrences of X and there is no limit for maximum occurrence.
X{n,m} – means at least n and at most m occurrences of X.
X+ - means one or more occurrences of X.
x*- means zero or more occurrences of X.