Block on the Periodic Table?
Below is a picture of the 4 blocks in the Periodic Table.  The elements in a block all use the same orbital to hold their valence or outer shell electrons.  For example, all of the elements in block 1 have their valence electrons in an $\ce{s}$ orbital, those in block 2 have their valence electrons in a $\ce{p}$ orbital, block 3 the $\ce{d}$ orbitals and block 4 the $\ce{f}$ orbitals.