Refers to fruit preserves, typically spread on bread or used in cooking. The English loanword is fully naturalized in Japanese.
朝食にパンにジャムを塗って食べた。
I spread jam on bread and ate it for breakfast.
This jam is made from strawberries.
I spread jam on bread and ate it.
I made jam with strawberries in the summer.
I slowly cook the fruit in a pot to turn it into jam.