We have been a few times now.
You have Disney:
Magic Kingdom (MK) all things Disney includes the castle.
EPCOT... (E) A park of 2 halves... All things future, plus the world showcase, lots of little live shows there too.
Hollywood studios (HS)... star wars is the big attraction, plus Toy story land and a thrill ride or 2.
Animal Kingdom (AK)... some rides, some animals, always our first park.
Then Typhoon Lagoon and Blizzard Beach... the 2 water parks.
Disney Springs, shopping, eating, bit of live music.
Disney resorts... you can visit all of the resort hotels, to eat or wander round. Some are on the monorail or the skyliner.
There are also the smaller attractions... mini golf Winter/Summerland and Fantasia
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Then Universal
Universal Studios (US) and Islands of Adventure(IOA)... the 2 theme parks, both have bits of Harry Potter stuff.
City Walk...restaurants, shopping, night life, mini golf etc.
Volcano Bay... water park, newish and excellent!
Then the resort hotels, again can be visited for food etc.
You can get combo tickets including Universal, Seaworld, Busch Gardens - (theme park near Tampa)and Aquatica (water park )
There is also Discovery Cove, Kennedy Space Centre, Wild Florida etc... depending on length of holiday.
You can buy tickets in many places. Would look at the ones on the Virgin/Tui/ BB holidays websites to get an idea of what each type offers.