My memory cached?

[aionshooter55]

when i press ctrl+alt+del it comes up with

physical memory
total 8180
cached 5417
available 5920
free 503

now it dont usually have that much cached when i boot my computer up i dont think it has any cached or mabey like 100 or something n free is usually alot more then that but im frequently running down to 3 free memory cached never goes down just constantly keeps going up how do i clear it??

 

[aionshooter55]

what i was trying to ask is do i need to clear it or does it just clear its self when its needed?

http://gpuz.techpowerup.com/12/11/01/gwr.png
http://gpuz.techpowerup.com/12/11/01/8gz.png

ok these pics here are of both the cards in my laptop the second 1 is a pic of my second card n its alway on 1mb usage n stuff does that matter that its never being used i think its ment to be but im not sure