A file that records the activity of a web server.

Log files can include this detail for each request:

 •date and time of the request
 •location of resource requested
 •server response to the request
 •IP address of requesting computer
 •user agent of requesting browser
 •referral string of requesting browser

...in addition to some more technical information.

Not every web server will be setup to display this information in exactly the same order. Look to the top of the log file for a line with "column" headings.