What's the difference between a gemspec summary and a gemspec description?

Question

When you write a gemspec file, what is the practical difference, if any, between the summary and description fields?

Answer 1

They are used in different places. summary is seen you do gem list -d, while description is seen on http://rubygems.org. Description "should be more detailed than summary" (http://guides.rubygems.org/specification-reference/), but in reality you see

s.description = s.summary 

in .gemspecs a lot.