>>359476949
Lighthouse is the IR laser emitter you need to have at least one for Vive or Index (and their controllers) to work. Two is the default amount, in opposite corners. You can get more (of the 2.0 lighthouses) to reduce occlusion problems and/or increase tracking volume, but two is definitely enough unless you are doing something weird.

What I meant if you want Vive Pro 2 you should buy Lighthouses (Base stations) from Steam and Index Controllers from Steam.