In the Dakotas, the word 'town' is more of a colloquial term. The requirements to be a town are basically that you have one of the following operating: post office, bar, or church. Really, because its so sparsely populated, it may also refer to an area of many square miles around one of the aforementioned establishments (even if they are no longer operational). It's just easier to say "My farm is in Roseglen" than it is to say "My farm is 30 miles northwest of Garrison" (which would be the closest town with an actual government, and businesses). Everybody from the area knows where you're talking about, and it helps locals preserve a bit of identity.

It may have a charter from the state. No idea what entitlements and obligations that brings with it, other than the highway department putting up "Now entering" and "Now leaving" signs.

I suppose it's the fact you won't have legislation between you and the state, i.e. you will have mayor powers over the rest of the population (if you ever get any) and whatever that entails.