Its and it's sound the same, but are used differently.
Use its when you mean "belonging to it."
The shark has very sharp teeth. Its jaw is also very strong.
The dog is digging for its bone.
The plant is in its pot.
Use it's when you mean "it is."
It's cloudy today.
Have you seen the beautiful cherry blossom tree? It's in front of the red building.
I have to go to bed now. It's my bedtime.