n8n is a tool for building automations by linking steps together visually. A typical flow might read when a form is submitted, look up the customer, create a task and send a message, each step handled by a connected app or service.
It is one of several tools of its kind, and one option is to run it on servers you control, which some businesses prefer for data handling reasons. Like any automation tool, it is only as good as the process it follows, and the flows need monitoring and maintenance so that failures are noticed rather than silently missed.