Where did my memory go? linux box

I just got a linux box and i installed apache, mono and i'm about to install mysql.

I checked the memory with free -mt and got this.

             total       used       free     shared    buffers     cached
Mem:           492        470         22          0         31        343

This means i have 492mb in total and i am using 470!?! how can i be using 470! i should only be running apache2. How do i figure out where my ram is going.

Answer

The -/+ buffers/cache displays the actual memory available on the free column. Linux uses unused memory for caching disk I/O.