What is France's "Great Shame of 2010" that they keep alluding to? Does "onside" mean the literal opposite of "offside," as in "not offside," or does it mean something else? Who are the kids that the players walk out of the tunnel with before kickoff? And at the end of the game match, I thought I saw players exchanging jerseys - is this a thing and can you explain it?

Edit: thanks for the answers to the above questions. My next question is when they give the player the red card - he's kicked out - does someone come off the bench to take his place?

Halp pls.

Edit 2: Asked and answered, thanks folks!