What Is "Description Vector" in Image Processing?
I think you have a matrix.
Each Row / Column is a descriptor vector of a point in the image.

Just like having features, let's say M features, and each point has M values corresponding to M features.

So each element in the descriptor vector is a value of specific feature for this point.

And yes, if you have M = 128 Features and 1000 points you'll get a matrix with 128,000 entries.