Core clock is how fast your GPU (graphics processing unit) is running at like a CPU which is displayed as Mhz or Ghz.
Memory clock is how fast your ram on your graphics card is running at.
Now you can increase these things to make your graphics card run faster then normal this is how you overclock your graphics card.
Normally the higher the Mhz of the core or memory the better.
I suggest you dont mess with them until you know what you doing first or you could fry your card.
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