A thing as a noun is an unspecified object e.g. “I need to get a few things from my room.”
The general situation you are in e.g.
“How are things? – things are good, thanks.”
- We have a thing going on – a casual relationship like in the song:
“Me and mrs Jones – we got a thing going on” - To do your thing – to live and act as you normally, routinely do e.g.
“I’m going home after work to do my thing” - To have “that thing” – a certain quality that is desired e.g.
“I can’t say exactly what it is but She just has that thing” –
in this case a quality that makes her attractive and interesting. - Thingy – a word used to describe a person or object you forget the name of: e.g. “Where is thingy, you know, what’s he called, John?” Or “I’m looking for that thingy, I left it on my desk somewhere.”