How do str/fai builds work?

I did strength in DS3 and that's what I started with for ER. Decided I wanted a bit more "flair" and options with a battle mage/paladin type deal and was recommended to try a str/faicbyikd but...I don't understand how damage scaling for the build works?

Level 60 27 vigor 35ish str 22 ish faith

Just enough dex and Other stats to be able to wield most of the weapons I've collected so far without paying attention to the outliers (nothing with over 18-20 requirements).

I've beaten rennala, been through a bit of caelid and faroth..got flame grant me strength and cragblade.

My current approach is using bloodhounds greatsword and I buff it with electrify/poison armaments and use FGMS for bosses but I don't think I'm optimizing.

Can someone ELI5 how str/fai builds work and maybe some stuff I can pick up to try