Replacing ceiling light, confused by wiring

[SUNRAY]

Exactly. They have a small tab on the bottom that touches the thread of a fully inserted lamp. The thread on the lamp holder is plastic or ceramic. Ceramic sockets can have metal threads but they‘re isolated from the supply too.

https://lightbulbsocket.com/wp-content/uploads/2017/10/wire-E27-lamp-holder.jpg

I've not seen anything looking like that yet. The modern versions I've encountered have an insulating female thread which tends to be just two opposite quarters of thread and easily cross threaded and near the end one of the thread segments is metal.
I don't have any here to sent a picture of.

 

[Ragnar_AT]

I think I know the type you’re talking about but haven‘t seen it in a long time.