Zombies are one of the original Minecraft mobs, having had several design changes over the years. They often appear on the surface of the Minecraft world at night as monsters that you often need to fight. New players may have trouble fighting mobs like zombies at first, but as they improve and grow more accustomed to the game and controls, it will become easier to survive the night. Many late-game players make "zombie farms" to gain EXP, or Experience Points. They may also use zombie farms to get the zombie flesh, as it is very useful to trade with Villagers. Because of all of this, zombies are a quintessential part of the Minecraft game.
Thank you for listening to my TED talk, and I'll see you next week to spend way too long typing up an essay about some more random shit.
Bye!