The main thing to look for in a modem is compatibility. Your internet provider will have a page on their website that lists ...

but DOCSIS 3.1 modems are typically more expensive. Other things to consider are the modem's speed limits -- make sure they're equal to or above your internet plan -- and the number of Ethernet ports.

Data Over Cable Service Interface Specification (DOCSIS) is an international telecommunications standard that permits the addition of high-bandwidth data transfer to an existing cable TV (CATV) system ...