The Term 'Expansion'?

I'm not sure where this should be posted as it can apply to any programming language as far as I can see.
I'm currently reading about Makefiles and there is a term used called 'Wildcard Expansion'. Also 'Link Library Expansion' etc. Any clues what is meant by expansion?

Here's a link to 'Wildcard Expansion' Wildcard Expansion. I'm really just trying to understand what 'Expansion' means?

Thanks