So what is going on in Lost for the past few seasons?

I used to watch that show all the time like four years ago until I just gave up from frustration but I'm considering picking it up again. Are they still on the island? Is that smoke monster thing still pissing around the island? Why was a polar bear on the island? Did they ever say what the Dharma Initiative was? Is the island magic or something? Who are the others? What was the deal with that invisible guy? I've got about 500 more questions but these are just a few...Lost confused the crap out of me but I would like to know what happened