Guitar scales question?

Question

What is a guitar scale? I thought it was playing the root note through ABCDEFG till I reach the same note, only an octave higher. Then I heard about penatonic, aeolian, and Ionian scales and now I'm confused. Whats the difference between the two types and which type would I be using to play in the correct key signature (C for example)?

Answer 1

There are thousands of scales in music.  

A scale is simply notes that will sound good together.  

Penatonic is a simplified Major / Minor scale, that a lot of rock used.  

Aeolian and Ionian scales are part of Modes.  There are 7 modes, and this is how you learn how to use all the frets of the guitar.

Answer 2

There is alot of scales the most popular is probably the c major scale