ある

あります says that a thing exists: "there is". The thing takes が, and the place, when you name it, comes first with に. あります is the polite form; ある is the form you find in a dictionary.

あります is for things

People and animals take います instead, in the same pattern. A cat is alive, so it goes with います. Plants do not move, and they take あります.

• × 庭に猫があります → 庭に猫がいます

Saying where a thing is

When the thing is already what you are talking about, it goes first with は, and the place comes after it: "the X is in Y". This is the order a question with どこ uses, and its answer.

Not there, was there

あります changes like any ます verb: ありません, ありました, ありませんでした.

Having

あります covers many of the things English says with "have": time, money, questions, a car. The thing you have "is there". The person, when named, takes は.

Usage notes

These go beyond saying that a thing is there.

Events

あります also says that something takes place: a class, a meeting, a party.

The place of an event takes で, because an event happens there rather than sits there.

• × 学校にパーティーがあります → 学校でパーティーがあります

Plain forms

ある conjugates as a regular う-verb except in the negative, which is the separate word ない. ×あらない does not exist.

• ある – there is
• ない – there is not
• あった – there was
• なかった – there was not