To the complete noob
Everyone here has at one time been a complete noob, so don't feel bad for one minute.
Citizen band operates in the 27 MHz band.
Most two-way radios (either commercial or public safety) operate on much higher frequencies, mostly from 150 MHz on up. Family Radio Service is in the UHF (460 MHz) range. Trunked radio services for public safety and other big agencies operate mostly in the 800 MHz range.
So you might notice that citizen band is in a (relatively) low frequency band, which means it is more subject to over-the-horizon propagation when the band is "open" ... this means in CB lingo that "the skip is rolling in." During some high points in the sun spot cycle (in the mid nineteen-seventies, for instance) skip would be solid all day at S 20 over 9. If you and the person you were trying to talk to were more than half a mile apart, you were out of luck because the skip would cover you up. And there were some really big stations with big linear amplifiers and antennas running skip. Right now the sunspot cycle is really really low and some folks speculate that it may not recover at all, so there is basically no "skip" on CB.
Nobody serious really considers citizen band a "two-way radio service."