Vim has four main modes: Normal mode, Insert mode, Visual mode, and Command mode. Normal mode is used for navigation and editing operations and is Vim's default mode; Insert mode is for entering text, accessed by pressing i, a, o, etc.; Visual mode is for selecting text blocks, accessed by pressing v, V, Ctrl+v; Command mode is for executing commands, accessed by pressing :. Mode switching is a core feature of Vim, separating navigation, editing, and command operations through different modes to improve editing efficiency. Candidates should be proficient in switching between modes, especially using the Esc key to return to Normal mode.