DSD wrote the interface for Avalara. When an order is entered with a tax schedule of AVATAX, it goes online and checks what taxes the ship-to address is subject to and adds it to the sales tax field on the totals tab. Other than address validation and tax recalc icons, nothing is added to Sage (besides the setup on LM\Setup). The AR Sales Tax report will show City, County, Special, State, etc. but the real detail is on the Avalara dashboard where it breaks it down by each jurisdiction.
A very high level overview...