Its or It’s

Use its as the possessive of (or belonging to) it.

Examples:
The doggie wags its tail.
Its color is brown.

Even though possessives of nouns (dog’s tail, man’s hat) have the apostrophe, its (as belonging to a thing or animal) one does not.

It’s is the contraction for it is and has an apostrophe.

Examples:
It’s cold outside. is the same as It is cold outside.
Now it’s raining.  is the same as Now it is raining.