A webhook is a realtime notification sent to your web server whenever an action occurs in the TI platform. For example, a learner completes a course within TI and you receive a realtime notification. You can then pass this event onward to any third party reporting/analytics system.
An SFTP Transfer is a nightly transfer of events from TI to a secure client FTP (SFTP) in CSV or JSON format. For example, every night on an automated basis, you could receive a file containing all course completions that occurred over the previous day.