What does it mean to invest in shares?

According to the SIAS Investment Guide Book, when you buy a share, you become a co-owner of a company, and if the company does well, share prices will generally increase.

As part of the co-ownership, common stock holders will have voting rights and a share in the company's profits through dividends and capital appreciation. To evaluate a stock, you may either use technical analysis which involves the use of charts, or fundamental analysis which involves analyzing company financials, management and prospects.

Source: SGX My Gateway