These are sometimes called bugs and are mistakes that have not been corrected by the software developer who created the program. In a commercial program that you buy from a dealer there should be very few errors. If you do come across a strange error message, telephone the dealer and he can tell you whether this is a bug or a mistake on your part. Bugs are the reason that software companies release patches which fix a particular bug or error in a program. Patches are normally available free from the manufacturer.
