Square is a mobile payment system that allows individuals and small businesses to accept credit card payments through a small card reader that plugs into a smartphone or tablet. Founded in 2009 by Jack Dorsey, Square has experienced rapid growth, processing over $2-10 million per week in transactions after signing up over 100,000 users in its first few months. Square aims to make payments easier for all parties by eliminating the need for cash or specialized payment terminals. The free card reader allows businesses to accept payments anywhere, and Square only charges a small transaction fee.