を
object (what the action is done to)
Noun + を + verb
Sign up free to review this point on a spaced schedule.
を marks the direct object: the thing an action is done to. 水を飲みます, "(I) drink water"; 本を読みます, "(I) read a book".
It's pronounced o, but written with its own kana, を. On a keyboard, type wo.
In casual speech を often drops out (水飲む?), but in writing and polite speech it stays.
を also marks a place you move through or leave: 公園を歩きます, "walk through the park"; 部屋を出ます, "leave the room".
What it doesn't mark is the thing liked, wanted or understood with 好き, ほしい and 分かる. Those take が, which catches out almost every learner at least once.
Examples
毎朝、水を飲みます。
I drink water every morning.
日本語の本を読んでいます。
I'm reading a Japanese book.
駅で写真を撮りました。
I took photos at the station.
公園を散歩しました。
I took a walk through the park.
七時に家を出ます。
I leave the house at seven.