I can tell you as a mechanical engineer with more than 30 years professional experience that there is no standard terminology or standard way to distinguish between "bolt" and "screw".
Of course there are wood screws, pointy with a slotted or Phillips head, and everyone calls those "screws". But pretty soon after that it gets weird.
Lag bolts are nothing more than big wood screws with a hex head, but they are called "bolts" - although I have also heard "lag screws".
For fasteners with machine threads, some people define "machine screws" as the smaller ones and "bolts" as the larger ones.
Some people claim that if it goes into a nut it's a bolt and if it goes into a female thread in another component it's a screw, but in that case what is it when it's lying on the workbench? Are you going to seriously tell me that in a bag of 50 pieces, 27 of them are bolts because I'm going to put them into nuts and 15 of them are screws because I'm going to screw them into other components, and the other 8 pieces don't have an identity till I attach them to whatever I end up attaching them to? What about cylinder head bolts for your car, which definitely do not screw into a nut, but which everyone calls cylinder head bolts?
"Socket head cap screws" - i.e., with a head for an Allen wrench - are generally called "SHCS" at all sizes and positions. But put a hex head on it and some authorities call it a bolt and others call it a screw.
If you are talking about putting a threaded fastener into wood, "screw" tends to imply a wood screw i.e. the female threads are formed directly in the wood, and "bolt" would to me imply either that you are putting a nut on the far side, or that there is a metal insert with machine threads. But, see all the above.
All of the above only applies in the US. I have no idea about the other English-speaking nations, nor about other languages.
Heaven preserve us.