Steam is a content delivery system and ecosystem for gaming, developed by Valve Software. It offers hundreds of games, from popular ones such as DOTA 2 to many other less popular and even obscure community games. Steam runs on Microsoft Windows, MacOS, and also Linux.
Current Supported Options
The current recommended method for running Steam on Funtoo is via use of Flatpak. The steps for setting this up are listed on the Flatpak page and will get you up and running with Steam. The Flatpak Steam image is based on Ubuntu 12.
In the past we have also offered a Docker image for Steam, but this method is no longer officially supported. See Steam/Docker for details on this image. It actually works very similarly to the Flatpak method, and interested developers may want to play with it or study it. It was missing some things like desktop icon integration. Since it requires a decent amount of work to maintain, and the Flatpak Steam image is actively maintained by others, and works well, Daniel Robbins decided it would be best to just use the Flatpak version as our official method.
While these two options use different technologies, under the hood they are actually quite similar. They both use a containerized version of Ubuntu which contains the SteamOS runtime.
History on Funtoo
Through Funtoo Linux 1.2, it was possible to play Steam directly under Funtoo. However, with the move to Funtoo Linux 1.3, 32-bit support was dropped from Funtoo, and Steam is currently dependent on a host of 32-bit libraries.
Thus, Steam no longer worked under Funtoo directly. However, it is still possible to run Steam under Funtoo via use of containerization technology. Initially, much of the setup was left to users to figure out. But now, there are officially supported options for Steam that are easy to set up.