Continuum in this context case is a line. You can map your architecture along this line.
How the generic solutions can be leveraged for your organization. You can grab these generic solutions from other companies and bring into your org and use them.
Enterprise continuum is really just a view of architecture repository. It is way of classifying items in your architecture as either being most generic or industry specific or common systems.
So in that line, most generic comes on the left and most specific goes to right.
There are 4 classifications withing enterprise continuum: