あります for things, います for living beings, where things are with に, and position words.
あります for non-living things, います for living beings (people, animals).
あそこに ぎんこうが あります。
There is a bank over there.
へやに ねこが います。
There is a cat in the room.
Both mean “there is/exists”. Choose by animacy: あります for objects, plants, events; います for people and animals. The thing that exists is marked with が.
に marks the location of existence: 机の上に 本が あります.
つくえの うえに ほんが あります。
There is a book on the desk.
The place of existence takes に (not で, which is for actions). Position words combine with の: 机の 上 (on the desk), いすの 下 (under the chair), 銀行の 前 (in front of the bank).
When the thing is the topic, use は…に あります: 銀行は 駅の前に あります.
ぎんこうは えきの まえに あります。
The bank is in front of the station.
Two patterns describe the same scene from different angles: place に N が あります (introduces a new thing) vs N は place に あります (tells where a known thing is).
や lists a few nouns as examples — “A, B and so on”. と gives the complete list.
はこの なかに てがみや しゃしんが あります。
In the box there are letters, photos and so on.
つくえの うえに ほんや ノートなどが あります。
On the desk there are books, notebooks and the like.
や picks a few items and implies there is more. など at the end of the list makes that explicit. Compare と: 手紙と 写真 = letters and photos, nothing else.