How does a laptops RAM and CPU define how much save space you've actually used and have?

I found that, upon buying it and setting it up, my MacBook Pro has 4GB of memory. However when I check my disk usage it says that I have 224.53 GB of free space. Is this from the cpu? I don't understand. I have far too much saved data on my laptop to believe that it is under 4GB so what's going on? Please answer in detail, I'm a little slow to understand these things.