Explanation
Perform an action in preparation for a future situation; 'to do something in advance'.
Formation
Verb-て form + おく
Detailed explanation
The ～ておく grammar point is used when you want to express performing an action in preparation for a future situation or to do something in advance. It is attached to the te-form of a verb and expresses the idea of doing something beforehand, as a preparatory action.
Examples
Eki de kippu wo katte okou.
Let's buy the tickets in advance at the station.
Ashita hayaku okiru tame ni, konban hayaku nete okimasu.
I will go to bed early tonight to wake up early tomorrow.
Shiken mae ni benkyou shite okanai to, shippai suru kamo shirenai.
If I don't study in advance before the exam, I might fail.
Kare ga touchaku suru mae ni, heya wo kirei ni souji shite okimashou.
Let's clean the room before he arrives.
Practice
Grammar content sourced from hanabira.org.