Difference between forwarding a domain and connecting a domain

Site URL: http://www.elbpapercutting.com

All,

I've searched for quite some time and I'm having trouble finding what the difference would be between these two. Hoping somebody can break it down easily.

I have http://www.elbpapercutting.com connected to https://www.birdmafia.com, so it goes to the homepage.    

I found that my domain registrar allows domain forwarding, so I'd like it to go to a specific page.  https://www.birdmafia.com/elb/process

Do I need to disconnect the domain first, then go to my domain registrar and do the forwarding, or will it just not work at all for a specific page since it's a 3rd party registrar and not squarespace?   Would there be any difference between forwarding the domain over connecting the domain?

Thanks for any info.

Attached photos: screenshot showing my connected domains, then my dns records for elbpapercutting.com, then my domain forwarding.