Is Earth the only known planet with life on it?

Earth has one natural satellite known as "the Moon" and many humanmade ones (swuch as Sputnik).
Yes. It has one. Its formal name is "Luna", but most people refer to it as "the moon".

If there were none, then the phrase "the moon" would have little meaning, whereas if there were

more than one, then the phrase "the moon" really wouldn't narrow it down too well.

Does your planet have any ?