Call them what you want: Lackeys, Servants, Henchmen/Henchwomen, Mooks, or Toadies; Minions are followers of a villain.

There are two kinds: The valuable kind and the disposable kind. One of the valuable kind is usually very powerful and leads the villain's forces for them; this type of minion is rare and the villain is usually enraged by their death.

The disposable kind is usually found in vast hordes; they are often weak and incompetent, dangerous only in these hordes. They are easily replaceable and the death of a few doesn't matter.

Usually, the minions are killed by the hero, the hero's army, or the hero's sidekick. Sometimes, the master villain will destroy them as punishment for incompetence. Sometimes, the minion will usually take over the master villain's place following the latter's death (for example: Megatron took over as leader of the Decepticons following the death of his master, The Fallen).