In response to Apple abandoning OpenGL and the mass move to using 64-bit operating systems, EA has made some changes to the Sims 4 ecosystem.
The players of Sims 4 now will be given a copy of the Sim 4 Legacy Pack. The Legacy pack is 32-bit and its offered for compatibility reasons. For fresh installs both can be installed side by side.
Apple is using a new API called Metal which forced EA to make changes. Sims 4 is available on the PC and Mac.
On the PC, Origin has the Legacy Pack in extras for the game. This will be free and it will trigger a download.
The PC version of the Sims 4 is 64-bit which is now common amongst modern games. 64-bit Windows is excellent, it has much easier memory management.
The version of Sims 4 on the gaming box is 64-bit so the legacy edition is handy for legacy game disks that may become available. DLC is 64-bit so the legacy edition is mostly useful for existing expansion disks.