What is RF?
Literally “Radio Frequency”. As a tag or adjective it generally means technologies using electromagnetic emissions within a specific range of frequencies, from a few kilohertz (LF) to a lot of gigahertz (SHF, EHF). There are technologies that call themselves RF below and above these frequencies (like terahertz waves), but I’m not convinced they are “radio” as that is commonly understood. Actually I used to be a bit iffy about radar and microwaves, but I guess we can accept those as RF these days. Above THz is the beginning of Infrared (IR) and from there on up it’s light, then radiation.