Being a movie star, and this applies to all of them, means being looked at from every possible direction. You are never left at peace, you're just fair game.
— Greta Garbo
You should be familiar by now with the formal media definition of star:
A star is a person whose image embodies a set of meanings (ie their image means a range of things that are separate from their personal/individual identity) that are instantly recognisable by an audience.
A star is not a real person. There is a real person behind the star, but they are merely the source of the star persona, the set of meanings which are attached to the image. The star persona may be a very complex thing, consisting of meanings drawn from the star's personal life, childhood, current relationships, behaviour with friends, as well as their performance or appearance on stage and screen.
A star persona is created when a person's image is endlessly represented and reproduced across a range of different media. An individual can become famous for something they do ( act, sing, dance, murder, go to the moon) but they will only become a star if they become part of the media discourse which surrounds us - this is something they may have to instigate or encourage themselves, by giving interviews, allowing photographers access to them, offering opinions, basically increasing their news values. It is possible for someone who is well known to become a star in an instant, as they do something memorable, or get lucky in public - think of the moment in Jerry Maguire when Tidwell makes such a showstopping recover from his KO. Representation is crucial to the development of a star persona as each replication of the image adds to (or detracts from) the star's meaning for the public.
Stars are important to audiences when it comes to choosing media texts, in a similar way to genre. If an audience likes a star (or genre), they are more likely to select texts containing that star. If they really like that star (or genre), they will ignore other factors like reviews or word of mouth and simply select on the basis of the star. You've been there in HMV. You know you have. You've bought a CD (or DVD) by someone because you liked the single. Or another one of their movies. And you wasted your money - admit it.
Stars are also important to the producers of media texts. Stars are bankable commodities - they can be relied upon to shift units and create profits. Because they have an audience and a following, they can, to a certain extent, guarantee sales, whether it's of one edition of a magazine or a trilogy of blockbuster movies.
To find out first hand what it is like to be a star, you can do no better than read a biography or autobiography of a star. Most big stars these days have an autobiography out before their mid-thirties (it runs into two volumes if you're Geri Halliwell) but the best picture of a star's life is often only pieced together after their death, when the true nature of the craziness that surrounded them becomes clear. Look in the library!!
Films about Stardom
Hollywood is very prone to navel-gazing, and frequently throws up movies about being a movie star. These are either biopics (biography movies based on the true story of a particular star) or generic movies about making it in the industry.
See how many of the E! True Hollywood Stories you can find. Also check out these film biographies.