To sniff means to breathe in quickly through your nose to smell something.
Sniffing is something animals and people do to learn about the world around them.
Examples:
The dog sniffed the flower.
She sniffed the air to see if she could smell cookies.
I sniffed the cake and it smelled good.
The cat sniffed the fish and wanted to eat it.
The bear sniffed the air and knew there was food nearby.
He sniffed the air and found the hidden flowers.