By default, every team member will receive a digest email summarizing recent changes to the project, such as newly uploaded files or files they need to approve. This email is only sent when there have been changes to the project.
You can control the frequency of this email, including switching it off completely, by clicking your name at the top right of the screen and going to Profile, then scrolling to Email Settings. The dropdown menu controls the maximum number of times per day you will receive a digest email, ranging from 0-4 times. This is a maximum setting and in most cases you will receive fewer.
You can also choose which events you would like to be alerted to, such as uploads or new comments. Any which are deselected will not appear in the digest. For instance, if you deselected upload notifications and the only new change to the project was an uploaded file, you will therefore not receive a digest.