The breakpoints buffer shows the existing breakpoints, watchpoints and catchpoints (see Breakpoints). It has these special commands, which mostly apply to the current breakpoint, the breakpoint which point is on.
gdb-toggle-breakpoint).
On a graphical display, this changes the color of a bullet in the
margin of a source buffer at the relevant line. This is red when
the breakpoint is enabled and grey when it is disabled. Text-only
terminals correspondingly display a ‘B’ or ‘b’.
gdb-delete-breakpoint).
gdb-goto-breakpoint).
When gdb-many-windows is non-nil, the breakpoints buffer
shares its window with the threads buffer. To switch from one to the
other click with Mouse-1 on the relevant button in the header
line.