Replit is an easy-to-use online platform that allows users to run their code in any programming language, including Python, Haskell, and esoteric languages like LOLCODE. With Replit, users can execute their code using the Run button or built-in Shell, check output in the Console, and use Multiplayer feature to share code with friends for help. The platform also offers debugging tools, including Replit AI, which can be used to step through code and solve errors, although there are special guidelines for using AI during Advent of Code. Users can create new Repls using language templates, experiment with different languages, and get support from the Replit community or staff members via the Ask Forum or official subreddit.