Both are very important nowadays. Antiviruses are programs which will protect you from viruses and malwares, which can enter in your computer through downloaded files or visiting sites. They will protect you and your device from information theft and critical damage. Some are Norton and Malwarebytes.
Internet security instead are programs like VPNs, they are made to prevent information theft and for protect privacy: every thing that we search, type or read can be controlled.
I am personally using https://veepn.com/ and keeping my privacy under control.