So where to begin? When purchasing your Disney tickets, you start with the Magic Your Way ticket. This is the base ticket you need to visit the four main Disney theme parks. In addition to this, you need to choose the number of days you wish to visit the parks. Tickets are available up to ten days. So if you buy a 5 day ticket, this will allow you five day entrances to one of the four parks.
As an additional purchase, you can add the Hopper option. This will allow you to visit more than one theme park on any given day. This affords you a little more flexibility, meaning you can visit Magic Kingdom in the morning and Epcot in the evening to see the fireworks. This would only count as one visit.
The next addition is the Waterpark Fun and More option. Waterpark Fun and More option allows you entry to the waterparks and other Disney attractions, such as DisneyQuest, without having to purchase additional entry tickets.
The final {addition is the No-Expiry option. When you first use your Disney Ticket, it will expire fourteen days from that date. If you add the No-Expiration option, any unused dates on your ticket will never expire. This means if you buy a ten-day ticket but only use five days, you'll have a further five days to use on your next vacation.
So they are the options when buying your tickets for Disney. When you make your purchase, plan in advance what you where you want to visit. For example, if you decide not to visit the waterparks, there would be no point adding the Waterpark and More option to your WDW ticket. If you'll decide only ever visit one park a day then the Hopper option will be a waste of the extra money. Inevitably, people over-purchase their tickets and waste money unecessarily.