What was a form of poetry which shakespeare used?

Shakespeare frequently composed in a literary form known as 'sonnets'--a particularized poetry with fourteen lines containing a stringent poetic arrangement.

The sonnets consist of three quatrains, each made up of four poetic lines and one conclusive rhyming couplet (two distinct poetic lines) to wrap up the sonnet:

Quatrain (4 poetic lines)

Quatrain (4 poetic lines)

Quatrain (4 poetic lines)

Rhyming Couplet (2 poetic lines)