Paint gun tip and advice

I’ve done a little paint spraying, not much. I acquired a Husky Pro paint gun from my late father. It has both suction and pressure feed, I can’t find a lot on it. I have a piece of wood trim For my house I would like to spray. New house, banged a piece of trim and everything else was sprayed in place so trying to match it up. So 1, what is the gun tip in the picture below for? And 2, It’s a sherwin Williams acrylic paint. I will stop by the store but I can’t find any thinning info. Is it worth my time to try and spray with this gun or am I better off looking at a real cheap airless sprayer.
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