What does this code mean?

I see this about everywhere in PICAXE codes.

b1= %00110000

what does the percent and all the numbers mean?

All this info is in the

All this info is in the manuals, only in more detail, so I suggest you make them your first port of call.
The % symbol indicates that the number following is a binary value, and the numbers are the binary value itself.

0 0 1 1 0 0 0 00 0 32

0 0 1   1  0 0 0 0

0 0 32 16 0 0 0 0

 

32 + 16 = 48