In CompleteFTP Professional and Enterprise MFT, an event is an action performed by a logged in user on the server, or an action performed by the server itself (a scheduled event). For example, uploading or downloading a file is an event.
Email notifications can be attached to these events, so that when, for example, a file is uploaded, an email is sent to a specified user providing details of the upload. Email notifications are described in more detail here.
Process triggers can also be attached to these events, so that when the event is triggered, a program can be launched. Process triggers are described in more detail here.
These events can also be recorded in the audit log. Note that email notifications, process triggers and auditing are not supported in the Standard Edition.