Vintage lenses on a modern Nikon?

I own a Nikon D3300 and have been experimenting with using older lenses. I have noticed that the camera responds differently to the lighting when using these older manual lenses. The biggest factor so far appears to be the ISO, by increasing it I have been able to get better exposures. I'm curious as to why this would be the case compared to when I use the kit lense.

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What does the letters mean in the Nikkor Lenses?

For example in

AF-S DX NIKKOR 35mm f/1.8G

What does G mean?

and so is the other letters
ED
D
IF
VR = vibration reduction

http://www.nikonusa.com/Find-Your-Nikon/Camera-Lenses/index.page

Thanks!

Read more: What does the letters mean in the Nikkor Lenses?