An API is a documented set of requests a program will accept, such as create a contact, list invoices, or update an order. An integration is the code or automation that calls those requests on one system and passes the results to another. It authenticates with an API key or OAuth, runs on a schedule or in response to a webhook, and translates fields between the two systems.
Most small businesses run several tools that do not share data on their own: a website, a CRM, accounting software, a booking system. Integrations keep them in step, so a customer entered once appears everywhere and reports draw on the same numbers. That removes duplicate entry and the errors that come with it, and it lets an event in one system start work in another.
Check that both systems actually offer an API and that your subscription level includes access. APIs have rate limits, change over time, and occasionally fail, so an integration needs error handling, logging, and someone responsible for maintaining it. Decide which system is the source of truth for each piece of data to avoid conflicting edits. Store API keys securely. We build and maintain integrations between the business systems clients already use.