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. In around 2016, the economics of Moore's law began to fail, perhaps partly due to skill issues by Intel, and cost per transistor is no longer falling cleanly. Density scaling is also slowing due to the difficulties of printing extremely small transistors. Much of the recent increase on the trendline above is in fact from using multiple silicon die rather than increased density.
Moore's law is often misinterpreted or misquoted as a statement about price or performance scaling.