Stacks are pre-defined configurations of engine9 designed for different verticals. Get up and running in minutes with common setups. Use terminology and technologies you're already familiar with, instead of changing your whole vocabulary and infrastructure for a new platform.

Contacts? Constituents?  Supporters? Donations? Transactions? Payments? Ugh, exhausting. Your definitions matter. They mean things. engine9 Stacks let you start with the terminology YOU use, not something from another sector that a sales dude told you "could be mapped" into your world.

Also, there is awesome technology you already use in your universe. Stacks let you connect these technologies easily, combining them with commonly used technologies in a common infrastructure that is usable immediately, not after "consulting engineers" spend months trying to integrate them.