The time signature is 6/8
That is a duplet. It works like a triplet, but instead of playing three notes in the time of two, you play these two in the time of three.
Another way to write this is by using dotted eights. But for example in 6/8 time, it's preferred to use duplets. It helps signifying how foreign the rhythm is in relation to the time signature you're in.
The dotted minim/half in the lower stave shows that 6 quavers/eights fit. So the "2" means "2 in the time of 3". It indicates an irregular group of notes; usually a higher number of notes have to be played in the time of a lower number, and thus quicker than notated; here we have the less usual situation where a lower number (2) have to be played in the time of a higher number (3), and thus slower than notated.
You can tell numbers that indicate irregular groups from fingerings: the former are italic.