How to use GNU debugger - gdb?

This is the GNU debugger. Usage:

gdb [options] [executable-file [core-file or process-id]]
gdb [options] --args executable-file [inferior-arguments ...]

Options:

--args Arguments after executable-file are passed to inferior
-b BAUDRATE Set serial port baud rate used for remote debugging.
--batch Exit after processing options.
--batch-silent As for --batch, but suppress all gdb stdout output.
--return-child-result
GDB exit code will be the child's exit code.
--cd=DIR Change current directory to DIR.
--command=FILE, -x Execute GDB commands from FILE.
--eval-command=COMMAND, -ex
Execute a single GDB command.
May be used multiple times and in conjunction
with --command.
--core=COREFILE Analyze the core dump COREFILE.
--pid=PID Attach to running process PID.
--dbx DBX compatibility mode.
--directory=DIR Search for source files in DIR.
--epoch Output information used by epoch emacs-GDB interface.
--exec=EXECFILE Use EXECFILE as the executable.
--fullname Output information used by emacs-GDB interface.
--help Print this message.
--interpreter=INTERP
Select a specific interpreter / user interface
-l TIMEOUT Set timeout in seconds for remote debugging.
--nw Do not use a window interface.
--nx Do not read .gdbinit file.
--quiet Do not print version number on startup.
--readnow Fully read symbol files on first access.
--se=FILE Use FILE as symbol file and executable file.
--symbols=SYMFILE Read symbols from SYMFILE.
--tty=TTY Use TTY for input/output by the program being debugged.
--tui Use a terminal user interface.
--version Print version information and then exit.
-w Use a window interface.
--write Set writing into executable and core files.
--xdb XDB compatibility mode.

At startup, GDB reads the following init files and executes their commands:
* system-wide init file: /etc/gdb/gdbinit