There are several ticket types.
1. A base ticket. Gets you into any ONE of Disney's four main theme parks (Magic Kingdom, Animal Kingdom, Epcot, Disney's Hollywood Studios) per day.
2. A Park Hopper ticket. Allows you to enter more than one of the four theme parks per day. Prices can change, but currently there is a flat $45 charge per ticket. For the same $45 you can add Hopping to a 1-day ticket or a 10-day ticket.
3. A Water Park Fun & More add-on. This is another flat fee option can be added to either a base ticket or a Park Hopper. The WPF&M option allows you a specific number of admissions to the Disney water parks or DisneyQuest. The number of WPF&M admissions you receive is equal to the number of days of theme park ticket you have. For example, if you have a four-day base ticket and purchase the WPF&M add-on, you will be given four admissions to the water parks or DisneyQuest. Currently, the WPF&M add-on costs $50 per ticket. The rate is the same if you have a 1-day theme park ticket or a 10-day theme park ticket.
Theme park admissions and WPF&M admissions are unrelated. To answer your specific question, if you have a base ticket with the WPF&M add-on, you can go to both ONE theme park and a water park or DQ in the same day. If you have a Park Hopper ticket you could go to two theme parks in a day, but not to a water park or DisneyQuest. If you have the Park Hopper with the WPF&M add-on, you can go to more than one theme park AND a water park or DQ.
You can find related questions
HERE,
HERE, and
HERE.