What is the function of the magnetic lasso?

[bwood]

Working on some logos I’ve stumbled upon this tool, but I really don’t understand what it does or how it works. By definition it ‘should’ lasso a graphic, or photo subject with a well defined background, and simply cinch up to the portion it’s looped around. We can trace, but I understand this tool is very old. Magnetic lasso is not mentioned in Xara pro documentation. Let’s say you wanted to isolate the moon in this photo. Can you use magnetic lasso? Or would you use other methods described in erase / mask etc.