Buying companies trading below what their assets and earnings suggest they are worth, on the expectation the gap closes. The starting screen is a low P/E or a P/B under 1, both sortable ascending on the PSEye explorer. The hard part is the second step: a low multiple can mean the market has overlooked a company, or that it correctly expects earnings to fall, and only reading the financial statements separates the two. It also asks for patience, since a gap can stay open for years.
See also
See every term in the full PSE investing glossary.