I think I can explain agile in three words; “uncovering better ways”.
These three words feature in the first sentence of the manifesto for agile software development. They are that important. They tell us the essence of agile.
Uncovering – Finding out as we go, not thinking we can know it all upfront.
Better – Always looking for improvements.
Ways – Tells us it’s a practice, it needs to be done, repeatedly, to make it work.