Some internet providers place a limit on the amount of data that each user can consume in a given month. This limit is often called a Data Cap.
The Internet service provider will monitor the internet data used each month and apply fees, slow down service, or shut off access.
The type of activities you enjoy online will determine how often you hit these barriers. Downloading video games or binge-streaming TV shows uses significantly more data than sending an email. Even activities such as browsing can add up if you have a large family that is online frequently.