I want to know what the structure is that is circled in red. I thought that it was to increase air to the engine and make it look it slick, but I was told it wasn't. What is the structure on this dodge charger?
It is indeed a hood scoop used to allow fresh clean air to enter the engine. For this application, the air filter was made to sit high enough to allow it to poke through the hood and was visible from the front. Here is a picture of what the under hood should look like (this is a Coronet, but should be something similar):
If you look at the black portion attached to the bottom of the hood, it seals the air filter unit so it only sucks the fresh outside air being ducted by the hood scoop. I believe this option was only on the Hemi powered models, but not sure about that. Also, you will see a lot of regular Chargers/Challengers with fiberglass reproduction hoods, which may not have the ducting present.
Another use case for similar structure:
Could be used to increase intercooler air circulation with turbocharged vehicles:
In this case it does not have anything to do with engine air intake (other than cooling down intake air), its sole purpose is just to cool down air flowing through it to engine. Intercoolers like this are often used with turbocharged engines because turbocharger compressor will heat up intake air.
Basically air flowing through hood scoop is used to cool down air that flows from atmosphere through air filter, turbocharger and intercooler to engine intake manifold (in that order).
Also, when air inside intercooler cools down its density increases and this effectively, with turbocharger, allows higher air volumes to be delivered to engine. Without intercooler, compression will heat up air and pressure required for same amount of hot air will get a lot higher than with air cooled down.