In general terms what does telecommunications include?

Answer 1

Voice and Data, a million protocols and hardware standards. Wiring, wired & wireless routers, switches. I don't do enough voice to tell you the device names. (Glass) fiber runs at tremendous speeds, if you can afford it. Some companies can, and can justify the cost. Cell phones, microwave and sattelite communications fall into the category also. Lots to learn about.

Telegraph may not be quite extinct. Some ham radio operators still use morse code. Cell phone text messages (can't remember the standard name) are not too dissimilar.

Answer 2

Everything. It is the mother of all communications. It's easier to say what isn't.

Your mailman
The Pony Express

It all started with Telegraph and that's gone now.