You might have some code that throws an exception (generates an error) like this:
errorMessage = sprintf('Error in function %s() at line %d.\n\nError Message:\n%s', ...
ME.stack(1).name, ME.stack(1).line, ME.message);
fprintf(1, '%s\n', errorMessage);
The error here is a string in ME.message. Parse it means that you might look at the error and try to recognize certain words and take action based upon what you find. For example you might have an error that says this:
Error using imread (line 349)
File "sss.dd" does not exist.
and you might want to do some particular thing, like alert the programmer that the file doesn't exist and to make sure the folder is prepended to the filename
if ~isempty(strfind('does not exist') )