を (wo) particle

を (wo) is one of the most commonly used particles in Japanese language.

- indicates a "direct object"
- is pronounced as "o" even though its written as を (wo)
- it describes an action upon an object
- it also describes things that are directly involved or affected by an event

object を event/action

Examples:
日本語を勉強します。(Nihongo o benkyou shimasu.)
I study Japanese.

きものを着ます。(Kimono o kimasu.)
I put on a Kimono.

足音を聞きます。(Ashioto o kikimasu.)
I hear footsteps.

トムさんはお茶を飲みます。(Tomu-san wa ocha o nomimasu.)
Tom drinks tea.

メアリーさんは電話を掛けます。(Mearii-san wa denwa o kakemasu.)
Mary dials a phone.