LMB stands for Left Mouse Button, which is a button on a computer mouse, including its left half. It is used for clicking, dragging, highlighting text, and opening files. The LMB is also an essential component of computer input devices and is located on the left side of a standard computer keyboard, mouse, or trackpad, and it is operated by the index finger. The LMB can be used to perform a left-click action without the need for a mouse. It is not a key on the keyboard, but it can be used in combination with keyboard shortcuts, such as Ctrl+LMB.