Īpple has used four series of CPU architectures in its Macintosh line of computers: the Motorola 68000 series, the PowerPC series, the Intel Core series, and its own series of ARM-type processors. The second version, introduced in 2020 as a component of macOS Big Sur, is part of the Mac transition from Intel processors to Apple silicon, allowing Intel applications to run on Apple silicon Macs. The first version of Rosetta, introduced in 2006 as a component of Mac OS X Tiger, was part of the Mac transition from PowerPC processors to Intel processors, allowing PowerPC applications to run on Intel-based Macs. The name 'Rosetta' is a reference to the Rosetta Stone, the artifact which enabled translation of Egyptian hieroglyphs.

It gives developers and consumers a transition period in which to update their application software to run on newer hardware, by 'translating' it to run on the different architecture. for macOS, an application compatibility layer between different instruction set architectures. Rosetta is a dynamic binary translator developed by Apple Inc.

PowerPC binary translation (original version) PowerPC application (Microsoft Word for Mac 2004) running on Mac OS X for Intel in Rosetta