Fuel Injection - explain this to me like I am 6 years old

Most of what you guys are saying is going over my head. I have not worked on a car in 45, years before I got this one. I have done all the work myself, short of rebuilding the engine, I would have done that myself but the shop was many months faster than I would have done it

Truthfully I am not into racing the car so I have not bothered to learn about the cam and such.
I have a MSD electronic ignition and the vacuum advance appears to be working just fine. It is hooked up to the port on the right of the carb. I do not remember which on that is, at this moment

The carb I am pretty sure is an Edelbrock 1406, I recently added new rods and jets on a friends suggestions, runs 100% better.

I did some additional tuning yesterday, seems improved. I was able to increase the vacuum about 13 lbs I am also having a hard time keeping my hand held tach operating. seems I have to open it up and do cleaning and soldering more than I should have to