Question

how does pitcher plant eat insects frog etc.

Answer 1

Your attached picture is useless but nevermind coming to the question ,
Your answer is :
The Pitcher plant has a trap like mouth it looks beautiful due to which insect attracts towards it , as soon as an insect come towards its mouth, the open hind closes and thus the insect gets trapped inside his body .
Hope it helps

Answer 2

With the help of its leaf and hairs inside it