A DNS cache (sometimes called a DNS resolver cache) is a temporary database maintained by a computer's operating system that contains records of all recent visits and attempted visits to websites and other Internet domains.
DNS cache poisoning – Computerphile
In other words, a DNS cache is simply a memory of recent DNS lookups that your computer can quickly refer to when trying to figure out how to load a website.
The Internet relies on the Domain Name System to maintain an index of all public websites and their associated IP addresses. Think of it as a phone book.
With a phone book, we don’t have to remember everyone’s phone number, which is the only way phones can communicate: with a number. Similarly, DNS is used so that we can avoid having to remember the IP address of every website, which is the only way network equipment can communicate with websites.
