WDW Magic Your Way "Base" tickets allow one major park (AK, EC, MK or Studio) per day. You can buy a base ticket from one day up to ten days in length. All tickets expire 14 days after first use unless the no expire option is purchased.
There are three possible options which can be purchased and added to a base ticket. You can buy any one, two, or all three.
Hopping allows you to go to more than one major park per day with no extra charge to your ticket.
Water Fun and More gives you between three and six entries into the five minor parks (BB, DQ, PI, TL, WWS). You can go to more than one minor park on one day, but each visit uses up an entry. The number of entries allowed is determined by the number of base days on the ticket.
No Expire will allow any unused major park days or minor park entries to be carried forward forever until used.
A few important facts to consider.
Any MYW ticket can be upgraded to add days and/or options until 14 days after first use. You cannot exceed ten days of entitlements. If you had purchased a three day ticket and decide, after the third day of use that you wanted to add two more days you could.
You cannot use a MYW ticket to enter more than one major park on any one day unless the ticket has the hopper option on it. If you make the attempt, the turnstile will not unlock, the Guest side of the turnstile will state "access denied", and the Greeter side will have on the top line ticket information and the bottom line stating "crossover not permitted". The Greeter will also be able to tell where and when you last used the ticket.
One last thing, if you go to buy the No Expire option the price will be based on the total number of entitlements on the ticket, not the number of days remaining. Also, if you had already paid for no expire and you want to add to the number of days you will not only pay the amount for the additional days, but also the difference in price for the no expire option.