收到 (shōu dào) means to receive or get something that was sent. 收 means to receive or collect and 到 is a result complement indicating successful receipt. It is used for letters, packages, messages, money, and information. In modern Chinese texting and social media, 收到 (understood / received) functions like Roger or Got it as an acknowledgement. The opposite is 发送 (fā sòng, to send).