Thanks, Taylor, for your question!
Good news: With the Park Hopper option you can visit all of the four parks as many times as you like, and it will only use up one day from your ticket!
Please be aware that if you don't have the park hopper option, you would not be allowed to enter a second park using the same multi-day ticket on the same day. If you want to enter two parks on the same day, you either need the park hopper option, or you need to buy a separate ticket (usually paying for the park hopper is the more economical option).
If you aren't sure if you will need the park hopper option, I'd recommend that you wait and see. You can always add the park hopper option to your ticket once you are at Walt Disney World, but you can't take it off once you purchase it.
If you want more info about tickets, click
HERE for further info from Disney.
If you have any follow-up questions, please feel free to submit them using the "ask Bret a question" link
on this page.