someone give me examples of puns in the play?and also explain the exploiting multiple meanings of words, or of similar-sounding words and stuff....

Aitself,
often thought to be the lowest form of wit, is itself a play on words.  Authors use them to add
meaning or complexity to their works by having their words take on more than one meaning.  Much
of the humor derived from is from Wilde's use of puns.

The title of the play is in itself a pun.  As the play concludes Jack says

On the contrary, Aunt Augusta,...