This is an entry in our Disneyland 101 Glossary: Disneyland Resort definitions in under 101 words, from Mouse Brief.
Disney refers to the chance to interact with characters—actors in costumes portraying characters from Disney entertainment—as “character experiences.” These may take the form of a reserved meal, a show or parade, spontaneous interactions in the parks or what many guests refer to as meet and greets: scheduled times and locations to have a brief personal interaction with one or a few characters. You can find these meet and greet opportunities listed under the “characters” tab in the Disneyland app: during the scheduled times, you may queue-up, as you would for an attraction, and follow the direction of attendant cast members.