A bundle is nothing but a collection of multiple movies. You can buy or rent a bundle just like you buy or rent a movie.
For a rented bundle, all the movies in the bundle will be available for streaming for a specific rental duration (usually 30 days after purchase but can vary from case to case basis).
Please note that once you start the playback for a movie in the rented bundle, it will expire after a specific duration (usually 48 hrs after playback but can vary from case to case basis). You can find the details about the rental duration of a movie on the respective movie and bundle details page.