An orbital is a standing wave of the electron around the nucleus, like the patterns a drumhead vibrates in. These are slices through the nucleus, with brightness showing where the electron is likely to be found. Red and blue are the two signs of the wave, which matter when atoms overlap to bond. Each step up in energy adds a node, a surface where the wave is zero. The name gives the shell number and the shape: s is round, p has two lobes, d has four lobes or lobes with a ring.