The Raspberry Pi has a lot of system information available like details about the CPU, the current temperature of the processor, the amount of memory and so on. Not all of the information is available in one place; however, if you know where to look, you can discover quite a lot of interesting data about your Pi.

Full article here:
Finding Your Raspberry Pi’s System Information (Make Tech Easier)
Related:
How to Overclock Your Raspberry Pi (Make Tech Easier)