たくさん

たくさん means "a lot" or "many". It goes in front of the verb, after the thing there is a lot of.

The noun keeps its own particle, が or を, and たくさん takes none. It works for things you count and things you don't, so no counter is needed.

An amount, not a degree

たくさん says how much there is or how much you do. It does not mean "very". ×たくさん高いです is wrong; an adjective takes とても.

たくさんの in front of a noun

Directly in front of a noun it needs の: たくさんのひと人, "many people". たくさんのひと人がいます and ひと人がたくさんいます mean the same thing, and both are everyday Japanese.

Usage notes

These go beyond saying how much there is.

もうたくさんです

Said on its own, もうたくさんです means "that's enough" – you have had as much as you can take, and you want no more.