Warm-blooded animals keep its body temperature the same no matter what the temperature outside is.

Birds and mammals (with a few exceptions) are warm-blooded animals.
They keep the inside of their bodies at a constant temperature.

Cold-blooded animals get warmer and colder based on the temperature outside. They take on the temperature of their surroundings.

Amphibians, arachnids, fish, insects and reptiles are cold-blooded animals.

Warm and cold blooded animals | Learn the difference
Via Kids Learning Videos

A minute with nature: warm-blooded and cold-blooded animals
By West Bloomfield Parks Naturalist Lauren Azoury
Via Civic Center TV

Cold blood versus warm blood | Science on the Web
Via Stuff to Blow Your Mind – HowStuffWorks