ATIS is a continuous recorded broadcast at a towered airport. It packages current airport and weather information, and it ends by telling you to advise on initial contact that you have the information, identified by a phonetic letter such as Information Golf. AWOS and ASOS are automated weather broadcasts. UNICOM is a person at the field who can give advisory airport information and does not issue an ATC clearance or a Part 107 authorization.
What each service actually is
A continuous recorded airport broadcast that closes with "Advise on initial contact you have Information Golf" is ATIS, the Automatic Terminal Information Service (AIM 4-1-13). The letter is the version of the recording. When the recording is replaced, the letter advances. Hearing Information Golf tells you which copy you listened to, so the controller can confirm you and the other traffic are working from the same briefing. ATIS is information. It does not authorize an aircraft to enter the traffic pattern, and it does not authorize a small unmanned aircraft to operate in controlled airspace.
AWOS (Automated Weather Observing System) and ASOS (Automated Surface Observing System) are automated weather. They broadcast computer-generated observations, commonly wind, visibility, sky condition, and altimeter setting, on a frequency published for that airport. The knowledge test groups ATIS, AWOS, and ASOS together as automated or recorded airport weather broadcasts. That grouping is about the product you hear: weather information, not a clearance desk. The practical split is still worth keeping. ATIS is a recorded airport briefing at a towered field, letter-coded, and it includes weather plus airport items. AWOS and ASOS are the automated weather readouts you will also find at many smaller airports.
UNICOM is neither of those broadcasts. It is a non-government advisory station, often the fuel desk or FBO, that answers when you call. On request it may give wind information, the recommended runway, and other field advisories (AIM 4-1-9). The recommended runway is an advisory. The operator is not air traffic control. UNICOM cannot issue a landing clearance, cannot issue radar vectors, and cannot issue a Part 107 airspace authorization.
Section 107.49 requires the remote pilot in command to assess local weather before flight. These broadcasts are one way to do that at an airport. A consumer app does not replace the need to know which aviation product you are listening to. Time stamps on these products are Zulu, covered on the Zulu time page, and the coded observation itself is a METAR.
How to use them on a drone job
Start with the Chart Supplement or the airport data block so you know which frequency is which. A line that lists CTAF/UNICOM on one frequency and AWOS-3 on another is telling you two different services. Traffic self-announcements belong on the CTAF. The weather computer belongs on the AWOS or ASOS frequency. Mixing them up means you are listening to wind while the airplane in the pattern is talking somewhere else.
At a towered airport, listen to ATIS before you form a picture of the active runway, wind, and airport notices. If you later talk to the tower, you report the letter so the controller knows which recording you have. The letter is not permission to launch. If the airport sits in Class B, C, D, or a Class E surface area, prior ATC authorization under §107.41 is a separate step. ATIS does not provide it.
At a non-towered field, call UNICOM only for what it can give: wind, the runway the local traffic is using, and similar field advisories. Treat the answer as a recommendation. You still yield to manned aircraft, and you still may not interfere with the traffic pattern under §107.43.
A morning at a towered field and a county strip
You are photographing a roof two miles from a Class D airport. The handheld picks up a continuous recording that ends, "Advise on initial contact you have Information Golf." You write down Golf, the wind, and the active runway, and you use that weather in the §107.49 assessment. Golf identifies the recording. It does not put the aircraft in the pattern, and it does not replace the authorization you need inside that Class D.
Later the same day you move to a small non-towered airport. You call the UNICOM station and ask for the wind and the runway in use. The person on the desk gives you both, as an advisory. You do not ask that station for an airspace authorization, and you do not treat the recommended runway as a clearance. If the Chart Supplement lists an AWOS frequency, you listen to that broadcast for the automated observation and keep the CTAF for traffic calls.
The traps these questions are built to catch
The lettered recording is the trap. MULTICOM is the self-announce frequency used where an airport has no tower, no Flight Service, and no UNICOM. It is not a continuous recorded broadcast named Information Golf. And ATIS is not a recorded clearance to enter the pattern. The correct reading is recorded airport and weather information, with the phonetic letter marking the current version.
The UNICOM trap offers three jobs a person at the field cannot do: an airspace authorization for a nearby drone flight, radar vectors to sequence traffic, and, by the same rule, a landing clearance. Wind and a recommended runway, advisory only, is the service UNICOM can provide.
The third trap is category, not detail. ATIS, AWOS, and ASOS are not thunderstorm types and they are not drone registration systems. They are automated or recorded airport weather broadcasts. Keep UNICOM out of that list. UNICOM is a person you call. The other three are broadcasts you monitor.
Work the radio items on the free practice test, and take the airport lessons in the course if the letter codes and frequencies still blur together.