The word 'satellite' is a noun, a word for a celestial body orbiting a planet; a man-made device placed in orbit around the earth, moon, or other planet; an organization or facility that is managed or controlled by a larger, often centrally located unit; a word for a thing.
The noun 'satellite' is a word for a small country or state politically or economically dependent on another; a word for a place.
Naturalism is a noun.
The Moon is the satellite of the earth
part of speech
The part of speech for this particular word is a noun.
adverb
what part of speech is work
what part of speech is beneath
the part of speech sashay is a averb
Did is a verb, and not is an adverb. Didn't is not any part of speech. It's a contraction of did and not.
Assuming no typo on your part regarding the "A" satellite, it would be that the moon was the first satellite orbiting earth. If you meant "why is the moon known as a satellite", it's because it is a satellite. Anything that orbits is a satellite.
Adjective
The word speech is a noun.