Think of MYW tickets like buffet items. You stack the items together to create a finished ticket.
DAYS - Daily admissions into the 4 theme parks. Only one DAY can be used per day. Base tickets come with 1-10 DAYS. A DAY will not allow you to go into more than one theme park per day unless you add the PARK HOPPER option (see below).
PLUSSES - A PLUS can be used for a one-day admission to one of the water parks, Pleasure Island, or DisneyQuest. You can use as many PLUSSES per day as you like, and you can use PLUSSES on the same day as a DAY, or on a day that you don't use a DAY. PLUSSES do not allow you to park hop; if you go into Blizzard Beach, that uses one PLUS, and if you go into Typhoon Lagoon, PI, or DQ on the same day, that uses another PLUS. You get a different number of PLUSSES depending on how many DAYS you got on the ticket:
1-3 DAYS = 3 PLUSSES
4-5 DAYS = 4 PLUSSES
6 DAYS = 5 PLUSSES
7-10 DAYS = 6 PLUSSES
NO-EXPIRY - Removes the 14-day expiration window from the entire ticket, including DAYS, PLUSSES, and HOPPER option. If you don't add this option, your ticket will expire 14 days after the first time you use it.
PARK HOPPER - This option affects your DAYS only, allowing you to visit more than one theme park on a day when you use any DAY of your ticket. If you don't get the HOPPER option, you cannot visit more than one theme park per day, since you cannot use more than one DAY per day.