The original Immigration category was replaced by the new top level Migration category recently. With that change, it was determined through the Categorization project that a new project should be started in order to better define the category structure.
While there are projects that do focus on specific Migration movements separately, there is no cohesiveness between the categories used. So the project in question here is not meant to lump all of the groups together, but to work towards a coherent and comprehensive structure that fits all movements, through either existing or future projects.
This would start by identifying the relevant migration events, linking out to existing projects, starting new focused projects, and also working on migration events that do not fit within a set project's focus (single family or individual migrations).