basically coins are a way to pay for a premium plurk account

if you get a coin, it lasts for a month. and during that time you get the extra features

one of which is you can have more emotes

And... How do you get those?

that's silly

you buy them, or someone gives you one

other features include: disable ads, extra colors for your display name, a "mentioned" tab to see the plurks where you've been @ mentioned, and I think different search functions maybe?

but yeah. another way to look at it: ad free plurking, and other perks.

As far as the extra emotes, it also gives you an interface to manage them into groups, so you can easily find what you're looking for.