I have my first diesel car, can someone please clarify something about glow plugs for me?

So I was aware with petrol cars they start up very easily because it just needs a spark and off you go. However with diesel you need to get it hot first and this would involve glow plugs. I realised today, I've never had an issue with the car starting up, does my car actually use glow plugs, or is it in only certain conditions like when it's really cold like -5? TIA