In a lot of posts i see someone mention playing a scale over a chord....What exactly does that mean??? I should probably know that already but i'm a little slow...

In western music, we have 12 tones.

A scale is just a choosen part of those tones. You can have 5 notes scales (pentatonics) up to 12 tones scales (chromatics) 4 and 3 notes are usually arpeggios, or chords. And under that, there's not much, so it's intervals.

Saying you play a scale over a chord is saying 'which set of notes do you use when playing over that set of 3/4 notes'.
Given the fact that music isn't exact, in the same situation, one will choose a set, while others will choose another one, while others don't have a clue because they don't know the corresponding set (or scale).

That's where mode theory start. Since a chord only has 3/4 notes, the scale you choose can be made with those 3/4 notes, but then, you can fill in the blanks. Depending on which notes you fill it in, you will play in a certain mode or another.

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Or, to take another interpretation of your post: playing a scale over a chord means what notes you play while (usually someone else) plays a particular chord. So, for instance, when someone plays a C major chord, you play a c major scale "over" it, in order to play a solo (however, this is being simplistic, you don't just play the scale from beginning to end, but you get my point, I hope).

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I understand now... Thanks a lot for the help