What Is The Difference Between Jelly And Jam?

For the past couple of weeks my kids have been complaining about the grape jelly I recently bought. We do toast with jelly and pb&j all the time so I know to always have it around. I kept telling them to get over it, it's Welch's, in my opinion the best, so just eat it and deal. lol Yesterday when I went to get a pb&j sandwich for myself I finally understood the complaints....

on the bottle it clearly reads Welch's Grape JAM! What the heck? I just grabbed what I thought was grape jelly at the store and apparently grabbed the jam by mistake. What is the difference between jelly and jam? Just for the record, I did not care for the jam either.