Example 1
窓が開けてある。
Mado ga akete aru.
The window has been opened (and remains open).
Breakdown
窓window
がsubject marker
開けてopen (te-form)
あるexists (result state)
Note: Implies someone opened the window intentionally, and it is still open.
Example 2
宿題がもう終わってある。
Shukudai ga mou owatte aru.
The homework has already been done (and remains that way).
Breakdown
宿題homework
がsubject marker
もうalready
終わってfinished (te-form)
あるexists (result state)
Note: Shows the homework was completed and is still in that state.
Example 3
洗濯物が全部干してある。
Sentakumono ga zenbu hoshite aru.
The laundry has been hung up to dry (and remains that way).
Breakdown
洗濯物laundry
がsubject marker
全部all
干してhang to dry (te-form)
あるexists (result state)
Note: Focuses on the fact that the laundry was hung up and is still hanging.
Example 4
この部屋はきれいに掃除してある。
Kono heya wa kirei ni souji shite aru.
This room has been cleaned (and remains clean).
Breakdown
このthis
部屋room
はtopic marker
きれいにcleanly
掃除してclean (te-form)
あるexists (result state)
Note: Emphasizes that the room was cleaned and is still in a clean state.