a hashtag is this: (#) and yes a lot of people brows on hashtags but only the most popular ones! but it is a good way to make more people than your followers to see your messsage!
yes! using hashtags will make your post more visible on search, especially when you use the trending one.
yes. hashtags are extremely popular. watch the hashtags that come up for the day and you can tell if there are opportunities for you.
You should always (or almost always) link a relevant hashtag in your tweets, just don't stuff your tweet with irrelevant popular hashtags.
Yes! Hash tags are the ones you tag using the number sign "#". It helps you get visible. It's the reason also why trends happen.
A lot of people use #(hashtag) so from what I've seen it is moderately effective, but no I don't really use them.
I think it depends on the person - and perhaps more importantly, the topic. But yeah, I browse hashtags occasionally.