I'm trying to parse this sign I saw at Beijing airport when catching the bus to Tianjin. The sign indicates where to buy the bus ticket.
清您先到13号门内省际购票厅购票
The hanzi 购 is confusing me. I'm now aware of three ways of saying "to buy":
Question: Is there a difference between 买 (mǎi), 购 (gòu), and 购买 (gòumǎi) which mean "to buy"?