"ITS" and "IT'S"

"Its" shows possession. "It's" is a contraction for "it is" or "it has." Ex.: The dog wagged its tail. It's a lovely day outside.

"ENSURE" and "INSURE"

"Ensure" means to guarantee or make certain. "Insure" refers to obtaining insurance coverage. Ex.: Please ensure the door is locked. We need to insure our new car.