An error is something that occurs when a program is in a state where it doesn't make sense to continue. An example is when a function is called with too few input arguments. In this situation the function should abort with an error message informing the user of the lacking input arguments.
Since an error can occur during the evaluation of a program, it is
very convenient to be able to detect that an error occurred, so that
the error can be fixed. This is possible with the
described in The try Statement.