Follow the work between the tools.
A booking arrives, a payment clears, and someone copies the details into another tab. That is the kind of handoff our integration work addresses. The website, payments, customer records, scheduling, inventory, email, and reporting can each have a place in a business process. What matters is understanding the particular connection your team needs.
Describe the process in ordinary language. What starts the work? Which system holds the information? Who needs it next? Where does someone check, retype, or correct it? Those details help define a useful project. They also separate the part that can be automated from the decision a person still needs to make.