Refreshing, in case there are more comments...

Here are my broad generalizations about various festival characteristics that aren't limited to any one country, from what I've seen and read, on this thread and elsewhere (I've only experienced events in North America):

Some festivals are enclosed + admission (at the gate or in advance)is required, some are free and open to all.

They may be mostly outdoors, mostly indoors, or both.
(Depends in part on the local climate, I suppose.)

They may be one-day, weekend, or week-long events.

They may focus on one genre (e.g., old-time or sea music), or encompass a wide variety of styles (including more or less variety in ethnicity of the music).

Some festivals have a dance component.

The number of and sort of participatory activities varies (sometimes a "workshop" is a panel of folks discussing/playing on a topic or theme, sometimes the attendees participate in some fashion).

Definitions of how wide the "folk" umbrella is vary from festival to festival.

There may or may not be nearby or on-site camping or other housing, and if there is this, this will increase the liklihood to near certaintly that there will be late-night music-making by attendees.

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Generalizations contrasting the US and UK, and I believe these apply to folk music-making in general, not just folk festivals:

Americans do less unaccompanied singing than those in the UK.

Americans do less group singing.

Americans do less drinking in association with music-making; certainly less public drinking.

Americans definitely do less drinking in association with dancing.

Other than that??

~ Becky in Tucson