Much like 'verb + ている', the 'verb + てある' pattern describes a resultant state. However, the similarities end there. てある is used exclusively with transitive verbs and puts the focus on the object and its current state, rather than on the person who performed the action.

The inclusion of ある indicates that the object is inanimate or cannot reverse the action done to it. Consequently, てある often describes a state that was intentionally created and can be translated as 'has been (verb)-ed' or 'is in a state of having been (verb)-ed', implying a specific purpose or preparation.

• メモは冷蔵庫(れいぞうこ)に貼(は)ってあるよ。
  I've stuck the memo on the fridge. (Literally 'the memo is in a state of having been stuck on the fridge')
• ヒーターはもうつけてある 。
  The heater has already been turned on. (Literally 'the heater is in the state of having been turned on')
• 映画(えいが)のチケットが買(か)ってある から心配(しんぱい)しないでね。
  The movie tickets have been bought, so don't worry. (Literally 'the tickets are in the state of having been bought')

The particle が can be used to mark the object when the verb describes an action done in advance or for a purpose. Some examples include:

確認(かくにん) - Confirmation (involves taking the time to confirm something).

調査(ちょうさ) - Investigation (involves taking the time to investigate).

説明(せつめい) - Explanation (involves taking the time to prepare an explanation).

For actions that do not imply this kind of prior arrangement (like closing a window), the particle を is generally favored for marking the object.