Agile: WHAT?

No ...

It is not a PM approach...but offer an approach also for PM concerns.

It is not an universal solution - silver bullet ...but it is a solution for many cases.
It is not a mindset...this is a mumbo-jumbo explanation, mostly when the right explanation is missing or when somebody make aggressive advertising. 

It is not easy... but the could offer also easy ways to manage some big problems.

It is not small... Agile related knowledge is not small, but is not centralized, "unified" and it is hard to understand that.

It is not Scrum...but Scrum it is Agile.

Yes...

It is a process approach... and demonstrated mostly for software development.
It is a cvasi-universal solution for adaptive problems...but there are some restrictions.
It is a response to Waterfall mindset... wrongly adopted by copy-paste to software development.
It is fragmented ... but you could start with the principles and the main methods.
It is easy to start and hard to master.