Describing a resulting state with intransitive ています, and completion/regret with てしまいます.
With a change-of-state intransitive verb, ています shows the state that resulted.
まどが われています。
The window is broken.
Intransitive verbs of change (割れる break, つく turn on, 開く open) + ています describe the current state, not an action in progress: 電気が ついています = the light is on.
てしまいます marks finishing something completely, or an unintended, regrettable result.
でんしゃに かばんを わすれてしまいました。
I (unfortunately) left my bag on the train.
Two nuances: doing something thoroughly/to completion (宿題を してしまいました = got the homework all done), or an unintended, regretted outcome. Casual contractions: 〜ちゃう / 〜じゃう.