API integration is the actual connection between two systems: mapping fields, handling authentication, deciding what happens when one end is unavailable, and keeping it working as both ends change. The API is the possibility; integration is the work.
Most of the value in a screen network arrives this way, because it removes recurring manual steps: prices, stock, staff rosters, customer records flowing in without anyone retyping them.
The caveat is that the build is a small fraction of the lifetime cost. An integration is a permanent dependency on somebody else's release schedule. The questions that decide whether it survives are whether the API is versioned, whether breaking changes are announced, and who is watching when it stops.
Design for failure explicitly. Retry with backoff, cache the last good value, and make a stale or missing feed visible to an operator rather than to a customer. The worst integration is not the one that breaks loudly. It is the one that quietly serves last month's prices for a fortnight.