What are poikilotherms and homeotherms?

Homeotherm has a temperature that doesn't change and pokilotherm is a temperature that changes according to the environment.

A poikilotherm is an organism that its temperature fluctuates based on the temperature of its surrounding.

Any animal (mammals, birds) that have some sort of internal heating device, keeping their internal temperature constant.

The English term 'homeotherm' means an animal that has a body temperature that is relatively constant and independent of the environmental temperature

Usually by 'basking' in direct sunlight, thus absorbing warmth. If they get too warm, they find a cool place to rest.