Didn't find this topic so......
I'm looking for an explanation for the suffixes that are at the end of program names,(eg- .exe,,,.dll,,,)etc. Can someone point me in the right direction?

Those 'suffixes' are called file extensions. They are used to specify the format of a file. For example, a file that has the extension .exe is an application ('exe' means that it's executable).
Here is what e.g. Wikipedia has to say about them. If you google the term "file extensions" you should be able to find more explanations if necessary.

Many thanks for the speedy reply.
I'll head over there and check it out.
Skypilot

Without the suffix, your computer will not be able to recognise the file format, and cannot open the file. Files may be pictures, words, graphs, etc, and the suffix tells the recipient computer what type of file it is. To open any file though, your computer will need to be programmed for that file type, and some programs may be incompatible anyway with your particular computer operating system, ie Mac vs PC. .exe files for instance are generally incompatible with mac programmes, so would have to be reformatted if the recepient computer was known to be a mac. Similarly some mac files would need to be reformatted for pc's.