disneycyclones

It's your SeaPass card on your wrist. Like a Disney MagicBand.
This explains more.
What are Royal Caribbean WOW Bands?
 
 
In addition to Royal Caribbean’s traditional SeaPass cards, select Royal Caribbean ships* also feature WOW Bands. These ready‑to‑wear, water-resistant wristbands require just one tap, so you can quickly and efficiently navigate the ship.
WOW Bands come equipped with RFID chips that enable guests to:
Unlock stateroom doors Make purchases at bars, onboard shops, and lounges Access lounges (Suite guests and Crown & Anchor members) Guests who wish to use a WOW Band in place of their SeaPass card may purchase one onboard for $4.99**. Guests in Grand Suites and above (Golden Suites & Royal Premiere for Spectrum of the Seas and Quantum of the Seas) will continue to receive the WOW Bands in their staterooms at no charge. WOW Bands are not reusable and are unique to each sailing.
For departure and boarding the ship in ports, guests will need a SeaPass card.
* Wow Bands are only available on Symphony of the Seas®, Harmony of the Seas®, Ovation of the Seas®, Anthem of the Seas®, Quantum of the Seas®, and Spectrum of the Seas®.
** Port taxes will be applied. Purchase price is subject to change without notice.

I'm new to RCL, what is WOW bands?

Sounds like there are many great food options. Thanks!

Johnny Rockets for breakfast only is included.  Solarium is included (buffet breakfast lunch, sit-down/buffet dinner).  Sorrentos is included.  Cafe Promenade food is included.  MiniBites is included.  DogHouse is included.  Windjammer (buffet) is included.  Main Dining Room (breakfast/lunch/dinner) is included.  Park Cafe is included.  

I was on Harmony in August and loved it.  I was in a suite and ate dinner each night in the suite restaurant (Coastal Kitchen).  I also at various times, enjoyed MiniBites, Park Cafe and Sorentos.  I did not eat in either the Solarium Bistro or Windjammer-the buffet options, due primarily to personal preference.  I am not a huge fan of buffets.  There is at least one other included option-the Dog House, but I don't like hot dogs, so I did not try it.  There are also a lot of specialty restaurants-my group did not try them because we were very content with the included options.  

You forgot about Johnny Rockets for breakfast.

Welcome @disneycyclones !
Check out my Harmony of the Seas Guide & Review, specifically the "Harmony of the Seas Dining and Restaurants" section.