What Does Multi Scale Image Analysis Mean?
Multi Scale means different scale of details of the image.
It comes from the intuition that blurring image with Gaussian Blur with $ \sigma $ vanishes data which is smaller then $ \frac{\sigma}{3} $.

In practice it is similar to Multi Rate Analysis of Filters in Signal Processing.
You look at the image in frequency domain and divide its data into octaves.
This partition can be done with any LPF Filter (Yet for perfect reconstruction there is some analysis).
In Image Processing the most widely used LPF is the Gaussian Blur.

By the way this is the idea behind Wavelets as well (Intuitively, in Wavelets they create special family of filters with certain set of properties).