The last 2 beats are triplets. The 3 with the bar above the notes denotes that. Basically, the way to view it is that the three triplets together make up 1 quarter note, so each is basically a 12th, rather than an 8th. Whereas 8th notes are counted 1-and, triplets are counted 1-and-uh (make sure you acknowledge the triplet feel with your foot when you're tapping).

Make sure you're playing each triplet evenly, so it's three 12th notes, not one 8th and two 16ths.

Tuplets are used to fit an odd number of evenly-paced notes into an even rhythm where they won't fit, and are referred to as irrational time. Wikipedia explains it pretty well, but feel free to ask for a deeper explanation.

http://en.wikipedia.org/wiki/Tuplet