# Glossary of terms

- **Card.** The primary component of an exploration. It consists of content and an interaction (where the content is text, images, videos, and other rich text components).
- **Category/Subject.** A category or subject that anyone can learn about on Oppia. Learners can choose from a list of categories on the home page.
- **Collection.** A group of explorations.
- **Community.** Anyone who teaches, learns, and contributes to any content on Oppia. Community members are respectful citizens whose main objective is to steward enriching learning opportunities.
- **Contributor.** Anyone who pitches in content for an exploration/lesson. One way that Oppia is more of a collaborative learning space, in contrast to more traditional online learning platforms.
- **Create.** To start an exploration/lesson in order to teach a topic
- **Creator.** A person who starts an exploration or lesson, a creator takes on the teaching role in the learning environment.
- **Exploration.** The fundamental unit of learning on Oppia. This is an interactive activity built by a creator, and consumed by a learner. 
- **Library.** The page where all explorations and collection on Oppia are displayed.
- **Interaction.** The interactive component of a card; this is the medium through which a learner communicates to a student by asking various types of questions and through which student can answer these question.
- **Learner.** A user who engages in an exploration or lesson.
- **Response.** Feedback and/or a new card that the learner is directed to based on their answer. A response can’t be empty; if a response doesn’t direct the learner to a new card, then feedback must be provided.
- **Rule.** A condition that triggers a response. Different interactions have different rule options. Multiple rules can be grouped together in a single answer group.
- **Tags.** Additional labels that can be added to an exploration in order to make it more findable in the gallery.