log (log file)

A log, in a computing context, is the automatically produced and time-stamped documentation of events relevant to a particular system. Virtually all software applications and systems produce log files.

A few common examples of logs: 

On a Web server, an access log lists all the individual files that people have requested from a website. These files will include the HTML files and their imbedded graphic images and any other associated files that get transmitted. From the server’s log files, an administrator can identify numbers of visitors, the domains from which they’re visiting, the number of requests for each page and usage patterns according to variables such as times of the day, week, month or year.

In Microsoft Exchange, a transaction log records all changes made to an Exchange database. Information  to be added to a mailbox database is first written to an Exchange transaction log. Afterwards, the contents of the transaction log are written to the Exchange Server database.

An audit log (also known as an audit trail) records chronological documentation of any activities that could have affected a particular operation or event. Details typically include the resources that were accessed, destination and source addresses, a timestamp and user login information for the person who accessed the resources.