In general and specific terms, who was William Shakespeare and why do you think a life in the theatre might have been attractive to him?

William Shakespeare was an English actor, poet, and playwright. His works were exceedingly successful in their own time and indeed were so influential that up until today, he is still undoubtedly the most famous playwright in history.
Because so many of the official records of his life (such as his birth and school records) are either missing altogether or have been lost, it is difficult to piece together specifics about Shakespeare's personal life. We do know something about his family: his father was a merchant and served as both alderman and bailiff (positions similar to a town mayor). He would have received free tuition at a local school and been given a good education (the school in Stratford, Shakespeare's hometown, is described as being even better than Eton at that time). This probably accounts for William's knowledge of Latin terms and familiarity with classical Greek literature, both of which we find often in his works.
While it is impossible to say exactly why Shakespeare decided to join the theatre in London, there are several possible reasons. Firstly, it is possible he needed funds at the time. With a wife and three children at home by the time he was twenty-one, Shakespeare may well have had a hard time supporting his family. Though not proven, it is believed by some that he went to London several years before joining the theatre looking for work and may even have been employed in some way at a theatre, such as in the stables as a horse attendant; from there he may have begun playing extras in plays until he was eventually recognized as an actor in his own right. It is also very possible that William, having learned and been drawn to classical literature and drama in school, wanted more than an ordinary life in Stratford could offer him. Married at age eighteen to a woman he may or may not have loved (they married in haste as she was pregnant at the time), William likely never had the chance to truly develop and use his talents before having to accept 'settling down' with a family; perhaps by the time ten years had passed, he knew he needed something more and joined the theatre to find it.
Whatever his reasons were, William Shakespeare became an almost instant success in the theatre, and his fame only continued to grow when his company, The Lord Chamberlain's Men, became a favorite of Queen Elizabeth. He wrote at least thirty-seven plays, 154 sonnets, and five long poems in his lifetime, and he literally invented English words still used today (some say we owe nearly 1,700 words to Shakespeare). The very fact that 400 years after his death, we continue to look to him as a beloved and unsurpassed master of drama and writing goes to show how truly important a person William Shakespeare was. We can still be grateful that, for whatever reason, he followed his heart to the theatre, living the motto he later wrote in the lines of Hamlet:

To thine own self be true, and it must follow, as the night the day, thou canst not then be false to any man.