Hi Robert!
Signature Dining refers to dining at Disney's fine dining establishments. Some of the signature dining restaurants include California Grille, Yachtsman Steakhouse, Jiko, Flying Fish Cafe, Narcoossee's, Citricos, and Artist Point. (This is not a complete list, but rather, some examples) Signature Dining restaurants require two table service credits from either the deluxe or standard dining plan.
Character Meals are simply, meals where characters are present and circulate around the tables and/or are available for guests to meet, take photos with and sign autographs. Some of the most popular character meals include Chef Mickey's, Ohana Character Breakfast, Cape May Buffet (breakfast), 1900 Park Fare (breakfast and dinner) and Crystal Palace. All of the character meals I listed require one table service credit per person. Cinderella's Royal Table (at the castle in the Magic Kingdom) is considered both a character meal and signature dining experience, and requires two credits. Most character meals are either buffet-style or family-style an are "all-you-care-to-eat". They are actually a good value, because people tend to eat enough for two meals :-) !
You can make reservations and enjoy both character meals and signature dining on both the deluxe and standard plans. The quick service plan includes only counter-style meals.
I hope my explanation helps. For a complete list of restaurants by category, click
HERE and you can search by the parameters that interest you on the left hand side.
Have a wonderful trip!