1) Value investing is defined as buying underpriced stocks and holding them until the market recognizes their true value, based on metrics like price-earnings ratios.
2) Value investing originated in the 1920s and was popularised by Benjamin Graham and David Dodd. One early practitioner was Roger Babson who used earnings multiples to determine "normal value".
3) There are different types of value investing including contrarian investing, cerebral value investing, passive/mechanical value investing, and activist value investing.