Although there are events in Edinburgh throughout the year, the biggest, and by far the best known is the Edinburgh Festival, which takes place throughout August at venues all over the city.
The season begins with the Royal Military Tattoo, which features displays by the various armed forces, and then there are several different arts celebrations which run concurrently all over the city and include film, comedy (the Fringe), music, folk music, cinema, literature, television, and theatre.
Events are showcases for new performers, and big names, and it's a good idea to check the events guide while you're in the city to ensure that you miss out on nothing that you want to see.