What is the embark framework? Who can use it, who should use it?
And what are the benefits?
Embark is a development framework. It's used to make development faster and more streamlined by providing a set of tools / functionalities to make you more productive.
In the case of embark it makes/will make the process of creating a dapp faster by simplifying the interaction between your app front end and the contract (e.g. running your own blockchain for development purposes out of the box, even if it's already pretty easy to run your own node, comes ethereum ready as far as front end, etc.)
Any person willing to make dapps should use it at some point IMO (or another framework) simply for the productivity value but also to test your dapp etc. As for using it now, ethereum technology being quite young I would still suggest first learning ethereum " the hard way " to better use it in the future and to understand what you are doing.
There is also Truffle that I've heard about but I didn't quite look into it yet as I have just started checking embark and am still doing things framework free.