Two Button Mouse

It shows a desktop mouse with separate left and right controls. In a message, that can label a control, a computer task, or a retro interface style.

The hardware came first. On May 2, 1983, Microsoft announced a two-button mouse for IBM-compatible personal computers, which followed IBM's PC design. In the Windows convention, the left button selects and the right opens a menu of options.

The drawing entered digital text through Wingdings, a symbol font for hardware and interface parts. Microsoft designed it in 1990 and 1991 and released it in 1992. A font mapping assigns this mouse the “mouse2button” label on the 8 key. Unicode brought many Wingdings and Webdings symbols into ordinary text in 2014. Apple historically favored one-button mice, while other systems used two or three; that older platform split gives the drawing a PC-era feel. In Word for Windows, entering 1F5B0 and pressing Alt+X turns the hexadecimal code into this character.

What does it mean when someone sends it?

Read it as a mouse or computer reference; context supplies any joke. If it arrives beside a request, respond to the words around it; the symbol alone does not say whether the sender is pleased, annoyed, or joking.