In more depth whats a stall converter do and how it works

[96_4.6]

I have the basics of how a stall converter works cause I'm not familar with this mod but come to find out I had my trans rebuit last week and they found a 3000 rpm stall converter and they rebuilt that too along with everything else. So the guy before me who had this car put a 3000 rpm stall converter on a stock 96 gt, I dont see why but oh well I put some mods on and now a stall converter too so I'd like to know more in depth whats the advanages and how it works. Thanks.