A stock split is when a company divides its existing shares into multiple shares to make them more affordable for small investors. Common split ratios are 1:2, 1:3, and 2:3. For example, HDFC shares priced at Rs. 3011.45 split 1:5 to Rs. 621.20 per share, and ITC shares priced at Rs. 905.80 split 1:10 to Rs. 93.50 per share. While a stock split decreases the share price, it does not affect the company's overall market capitalization or underlying fundamentals.