1, 2, 3... denote the energy level

s, p, d, f... denote the shape of the orbital

-these orbital shapes are around the x, y, z axes

How much each orbital holds (within each orbital is two electrons max):

s: 2 (1 spot)

p: 6 (3 spots)

d: 10 (5 spots)

f: 14 (7 spots)

But electrons want to stay in the smallest energy levels (1 > 2 > 3 >...)

Electron filling pattern: 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d,...