does the apple watch use data?

I think this answer should be more of a yes than a no. 

@mbrown877 Technically the watch is not accessing the cellular network, it's asking the iPhone to use make a request to use the iPhone's cellular data, but the result of that request is using your AT&T data. Isn't that really what you want to know? Is data being used?

Saying the Apple Watch doesn't use cellular data is sort of like saying my laptop doesn't use cellular data, when my laptop tethers to my iPhone it asks my iPhone to use it's cellular data whenever the laptop wants anything from the internet (technically the laptop is not using the data, the iPhone is).  

The Apple Watch accesses the iPhone's cellular data whenever it does anything that requires internet access when your iPhone is on Cellular (not WiFi).   

Siri, Weather, Maps, Messages (that are iMessage and not text messages), Shazam, sports scores, tapping / sketching (where you draw on someone's watch), audio messages, Shazam, and more...  

This is not much data, it's not streaming video, it's not a lot of photos, but it is data. 

Probably for anything like your contacts, callendar and personal things it just gets them from your phone via their connection.

If the iPhone has data over WiFi, the watch uses that (and not cellular, just like the iPhone), actually I think it can sometimes use WiFi without the iPhone.

Again, I'm sure it's not a lot, but my Apple Watch has the temperature on the watch face, that's constantly changing so it's constantly getting updates over the internet and when I'm not home that's cellular data.

In the settings app in your usage, you can look up the watch, but mine only says 14MB for the last 8+ months, that must(?) be just the watch app. I'd guess that the data that it asks individual apps would be reported under those apps.