Hi
I always think it's a shame that parents worry and fret more about their 'babies' starting school than the kids do! No one expects parents to be knowledgeable about school, curriculum etc, but I'm sure in due course things will be explained to you (if the school is any good at all at least) either in pre-Reception meetings, or in newsletters etc. And I'm afraid things are always changing: I haven't looked at it yet, but Pearson Education have a paragraph at top of this site about latest developments.
I was a Teaching Assistant (male) for twelve years, mostly in an Infant School, but I started as a parent helper when our DS was in Reception. What a Reception teacher WILL expect however is that a child can cope with the toilet, washing hands, eating lunch, changing for PE, waiting turns and sharing, handling books and equipment with a degree of care. And most of these skills DD should be starting to learn at Nursery.
juniper has already explained Key Stages and some Numeracy. All I would add to that is that counting REAL objects - say, dolls - then adding one more, taking two away, etc is better than writing numbers on a page. Have a Dolls' Tea Party: how many plates, cups are needed, how many biscuits, cut a large cake in two (half) in four (quarters) . . . I'm sure you're getting the idea!!
Reading and Phonics does require that you know the appropriate letter SOUNDS; and don't bother with letter names at this stage. Your Nursery staff SHOULD know these sounds, but I have heard plenty of otherwise capable teachers, who still get some wrong.
In particular: S is 'sssss' not 'suh' (as it used to be) and some schemes use a hand-weaving motion for 'ssss-snake'.
M is 'mmmmm' (rubbing tummy for nice food) not 'muh'.
N is 'nnnnn' not 'nuh'.
You can probably find them all on line somewhere, and there are CDs and DVDs available.
(I believe BT Outreach used to do free resources, but that may have ended.)
Good luck, and Enjoy it with DD!