Moore's law was the observation (by Gordon Moore, co-founder of Intel) that the number of transistors in an integrated circuit doubled every 18 months. This has, to some extent, held up, but only with significant changes in the definition of an "integrated circuit". In around 2006, the closely related Dennard scaling, which made power efficiency scale with density, failed, forcing a transition from faster single-core processors to more cores.
Moore's law is often misinterpreted or misquoted as a statement about price or performance scaling.