Interactions are a unified way provided by Discord to handle slash commands and component interactions, such as clicking a button. Slash commands are much better than message commands as they are not rate limited as much, meaning your bot can handle a lot more at once. They also contain a lot of data about a command, for example by making a command take a user as a parameter, the entire user object will be contained in the interaction so you do not have to fetch it yourself, avoiding even more rate limits!