System logs will show every event on an operating system. This is very useful to find if some one accessed the system, among many other things.
In computing, a logfile is a file that records either events that occur in an operating system or other software runs, or messages between different users of a communication software. Logging is the act of keeping a log. In the simplest case, messages are written to a single logfile.
A transaction log is a file (i.e., log) of the communications (i.e., transactions) between a system and the users of that system, or a data collection method …