What is a West Marches game?

[Eyes of Nine]

I want to know what West Marches discord's y'all were in. Its something I've always wanted to do but its hard to tell a good game apart from the mediocre ones, especially when it comes to a nebulous "discord."

I've participated in two different West Marches campaigns run by Jason Lutes of Freebooters on the Frontier fame (and if you are an indie comics fan, Berlin). He had discords for both. A ton of stuff happened on those discords.