What is the primary use of a firewall?

The primary use of a firewall is to prevent unauthorized access to or from a private network. Firewalls act as a barrier between trusted internal networks and untrusted external networks, such as the internet. They monitor and control incoming and outgoing network traffic based on predetermined security rules. By doing so, firewalls help protect sensitive data and systems from attacks, unauthorized users, and malware. This protective function is crucial for maintaining the security of both individual devices and entire networks.

The other options describe functions that are either secondary to the primary role of firewalls or unrelated. While limiting access to certain websites might be a feature of some firewalls, it is not the primary purpose as they are primarily focused on preventing unauthorized access. Similarly, running multiple applications simultaneously is more about resource management within a system rather than network security. Delivering content over the internet pertains to functions like web servers and content delivery networks, rather than what firewalls are designed to accomplish.