What is the difference between the regular feed and the "recent activity" sidebar/under list thingy?

The regular feed seems to be doing the same thing for me

The regular feed posts questions in the order that they have been asked.
The Recent Activity posts everyone's responses to those questions highlighting the persons that have been responding.
Questions with more responses will keep coming up in recent activity.
Also I think that you will see your friends more often but Im not sure.