CB radio Transmissions do not require a licence.
CB radio is AM or SSB.
CB radios use channels instead of dialing a frequency.
These channels all fall near 27 MHZ (HF Band).
You are not legally allowed to communicate with someone
that is more than Apx. 150 miles away from you.
CB can be used for commercial perposes.
Amateur radio Transmissions require you to have a licence from the FCC.
Amateur radio has many "modes" that you can use,
Am, SSB, CW (morse code), FM, and a few digital modes.
Amature radio has bands you can operate in MF, HF, VHF, UHF, and above into even "microwaves".
Amateur radios don't have cnannels, you acually set
the frequency number.
There is no restiction on how far away someone is you talk to. There are even people who "bounce" signals
off the Moon and back to earth.
You can not use a Amateur radio for business or for any communications were you would profit ($) in any way.
Those are the main things that come to mind.
Take care !,