Market capitalization, also commonly referred to as “market cap,” is a common term thrown around by investors that many people think to be complex, but it’s extremely important.In reality, it's a simple metric that investors use to evaluate publicly traded companies, and, in my opinion, it gets way too much attention.That said, you should know what a company's market cap is…but you shouldn't base your investment decision on it alone.Here, we'll define what market capitalization is, why it's important, how to calculate it, and, most importantly, how and when to use it as part of your investment strategy. We'll also touch on the various market caps a company can have—large-cap, mid-cap, small-cap, and more.