Is Key the same as Pitch?

No, they're not! Pitch is the highness or lowness of a specific note, typically expressed as a pitch letter name and octave number (like A4). You may play in the key of A major, for example, which means that: A will serve as "home base" (musicians call that the "tonic"); and the music will be built on the A major scale (comprised of the pitches A B C# D E F# and G#). 

Please see here for a beginner lesson on music theory: https://www.youtube.com/watch?v=xp8FVRqu7Zk

So you mean A to G are pitches and every key is made up of 8 notes?

Yes, although the 8th note is the same as the 1st (A and A, in the example above). The pitches in a key (and in a scale) repeat every octave. 

This may help: https://piano-music-theory.com/2016/05/31/major-scales/.

You said in a video that a key is a set of pitches played together so is a key a set of 8 pitches or a key is a set of any number of pitches? Which is which?

A key (in Western music) is a set of 7 pitches, with the 8th being the start of the next octave!

For example, the key of C includes C, D, E, F, G, A, and B. The reason we might say "8" instead of "7" is because the C major scale goes from C to C (CDEFGABC). 

I hope that helps. Music theory can be tricky to grasp (and explain in a simple, succinct way)!

Okay I get it. Not to bother you but in one of your videos you said "starting in the key of C" and you played less than 7 pitches. 

So if the pitches played are less than 7 it is not a key?

You can play any amount of pitches! For example, the melody of "Mary had a little lamb" in the key of C would be:

E D C D E E E, D D D, E G G, E D C D E E E E D D E D C

Those are only 4 pitches, but they all belong in the key of C, and the melody gravitates around the pitch C. 

If I wanted to play a full major scale, however, I'd need to play these pitches in succession: C D E F G A B and C (one octave higher). 

Hope that helps!

You said the pitches of the melody of "Mary had a little lamb" is in the key of C and in one of your videos you mentioned that the name of the key is determined by the starting pitch but the pitches of the melody "Mary had a little lamb" you texted there didn't start with pitch C.