encryption – When logging into my work WiFi (we are allowed to do this) what exactly can they see?

My work let’s us log onto their WiFi on our personal phones, we don’t have to log on every time it just connects automatically. I have nothing downloaded on my phone from my work which they could ‘spy’ on me with.

Am I right in thinking if it is a secure site, for example google.com if I search lets say for Facebook on the google domain it would just come up as google.com on the network traffic log providing there was no man in the middle attack from my employer?

Which brings me onto my next question,
how do you know if your employer is doing man in the middle attacks?