POA and 50% shared ownership?

We are looking into housing in the UK and have run across a few terms that are unfamiliar to me.  Does anyone know what POA is?  Or 50% shared ownership?  I'm not great at this stuff in the US and definitely don't know any terminology in the UK!!  Also, what does it mean when it reads that it has a £22,000 premium?  They make it sound like a benefit, but I can't tell what it means!

POA =Price on Application ( i.e. ask the agent and they will tell you the price )
Shared ownership usually means that you buy part of the property and rent the rest - this can be a way to afford a better property than you usually could.
Not sure what Premium refers to

Hope this helps

Melly

Thanks!  That clears up a bit of my questions!  I was getting a tad bit confused with all the lingo!