What does the <% operator mean in Scala generics?

In specs2 there is a method called Around, documented here that has the following example:

object http extends Around {
  def around[T <% Result](t: =>T) = openHttpSession("test") {
    t  // execute t inside a http session
  }
}

The source for this code can be found here.

I'm curious what the <% operator means in this context?

EDIT: here is a solid answer on this subject, What are Scala context and view bounds?