A Safe
Vault
noun
Gold storage is where you put your gold. You want it to be safe, so you put it in a safe or a vault.
金庫 can refer to various types of secure storage. Depending on the context, it can mean a personal safe, a bank vault, or a safety deposit box.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
家に金庫はありますか？
Do you have a safe in your home?
マミは貸金庫にベーコンをあずけているらしいよ。
Apparently Mami keeps her bacon in a safe-deposit box.
あの銀行の金庫はとても頑丈です。
That bank vault is very sturdy.