What are small cap stocks?

Small cap stocks are equities that trade on the public market, meaning all investors with brokerage accounts can buy them. What makes small cap stocks unqiue from many of the other high flyer coporations that are commonly known,is their valuation and by that I mean market cap. While there are some differences in what is the maximum market cap, it is generally $2 Billion. Often times though you see the indexes and ETFS contain companies that are maximum of $4 Billion.