Five years ago I wrote this answer that I'm not altogether happy with, but might go some ways to answering your question.

In short, "Guild" is a generic catchall term used to denote the phenomenon of professional associations in Medieval Europe. These professional associations set prices (fundamentally organizing local cartels) as well as offering job training and social security. Sometimes the Guilds were politically enfranchised, and at different times could have formal representation in city government (I offer some examples in the answer I linked, but every city differed in its own way). "Guids" are intimately tied to the individual urban communities they emerged in.