Reasons for splitting stock
The purpose of a split is to improve the liquidity of a stock: the more shares in issue, the easier it is to match buyers and sellers.
A company will sometimes announce a stock split when its share price gets so high that it prevents further investment. By dividing the stock, the company cuts the share price and makes the stock more affordable.
Lower prices tend to be more attractive to investors and often a stock split will encourage buying which often drives the share price higher again.
Bonus issue
A bonus issue (or scrip issue) is a stock split in which a company issues new shares without charge in order to bring its issued capital (outstanding stock) in line with its employed capital (the increased capital available to the company after profit).