The honest version of "does it integrate with my software." These are the systems this industry actually runs on, and what each one means for a build.
Bloomerang / DonorPerfect / Little Green LightDonor management
The systems of record for donors, gifts, campaigns and engagement in small and mid-size organizations, with accessible interfaces.
Salesforce Nonprofit CloudCRM
Where larger or more complex organizations track constituents, programs and grants, with extensive integration capability and correspondingly more configuration.
Grant managementFunding
Applications, reporting deadlines and restricted fund tracking, frequently maintained in a spreadsheet against portals that each work differently.
Payment and giving platformsRevenue
Online giving pages, recurring gifts, peer-to-peer and event platforms, each depositing and reporting separately.
Volunteer managementProgram
Scheduling, hours tracking and background checks for a workforce that turns over constantly and is not paid.
Program and case dataOutcomes
Whatever holds who was served and what happened, which funders increasingly require and which is often the least structured data in the organization.
AccountingFinance
QuickBooks or a fund accounting system, needing restricted and unrestricted funds tracked separately.
Email and communicationsEngagement
Mass email and newsletters, usually segmented far less than the donor data would allow.