Note: This review addresses v1.41 of the software.
A long time ago--a very long time ago--you always knew what chip was in your computer. (It was a 6502 or an 8086). Times have changed. Not only are there multiple major manufacturers of Pentium-compatible chips, even within a single chip family, there are dozens of variants and options. CPU-Z is a freeware utility that will give you detailed information on your CPU and RAM, including speed tests.
CPU-Z is trivially easy to use--double click the program and look at the results. CPU, cache, memory, and more are all displayed. Once you're done looking, you can dump the results to HTML or text. This can be handy in a corporate environment to keep track of which machines have which capabilities. On a personal level, it can be good to know exactly what you've got under the hood and what features it has; tech support often wants to know.
Note: This program is donationware. It is free to use, but the author accepts and encourages donations towards further development.