Inform vs. Notify vs. Brief

In English, when you want to tell someone about something officially or formally, you can use the following words:

Inform
Inform someone : When he arrived, inform me immediately.
Inform someone of/about : Why didn't you inform me of his arrival/death
Inform someone that: She informed me that she had not changed her plans.
Well- informed:He was never dull, always erudite and well-informed.

Notice that inform must have a direct object :
He informed me that he would not be able to come.
Don't say: He formed that he would never come.

Notify :
Notify is more formal than inform.

Notify someone:They were expected to notify us when they changed their plans.
Notify someone of/about : The company notified us of /about the inauguration date of its new system.

Brief
The verb means to give someone all the necessary information or instructions you need about a situation/a serious matter/a piece of work,before you do it or consider it.

- He briefed the new spies about/on their mission.
- We had already been briefed about/on what the job would entail.
- The Prime Minister has been briefed by her parliamentary aids.