You give the antitetanus serum because it contains passive antibodies that can immediately start attacking any antigens if present. While that is going on, the body reacts to the toxoids injected...
Tetanus toxoid is what a tetanus vaccine contains. You're body will make anti-bodies to tetanus once given the tetanus vaccine, offering you protection for "up to" 10 years from the bacterial disease...
Tetox is part of a number of vaccines given to babies. It is repeated every 10 years. If there was an injury which may be tetanus prone (a dirty wound, or a puncture wound) and it had been 5 years...