Users from Chrome Web Store - who are they?

Issue, that bothers me: every day 10-15 people adds my application via Chrome Store.

But I don't feel like they are using website or coming back (and bounce rate among them is nearly 100%).

From another point, it doesn't seem to be ok to add website to your bookmarks without any intention to use in future.

So what does it mean, finally? Do this people just 'pick it up, coz it free', or I can hope that these people eventually will become users?

Well I think you got a few points to look at

1. What are your analytics like? Do you know the users location, browser types etc? What pages are they viewing last? are they just going to home page and leaving? why? how is it marketed, what is bringing them there and making them leave? Questions like this should generally be a collective efforts, show your friends the "way in" (app, ad, etc) and the landing page. Ask them to honestly tell whether or not they will stay on that page and why?

2. You mentioned Chrome Store. What are you publishing on the Chrome Store? Is the app meant to constantly interact with the site? Why does the app exist if users are meant to use the site? If the app is independent of the site, then there is no reason for them, to visit. Are you forcing visits? I.E. redirect once download complete? In that case there is no question, why you have a high bounce rate.

3. App tracking. Are the users keeping the app or deleting after download? Are they using it daily, weekly, etc? Can you monetize the app independent of the site?

These aren't questions I am asking you, these are questions you need to ask yourself, and if you don't have an answer, implement solutions to find out.