Vim has three different visual modes to work with characters, lines, or
rectangle blocks of text. We can switch between these modes by pressing v,
V, or <ctrl-v> respectively.
Many a times, we select something and press ESC by mistake, it is annoying to
reselect the whole block of text again by pressing v/V. Vim provides a command
gv to reselect the range of text that was selected. Command gv works for all
the visual modes.