Forget the textbook image of electrons orbiting the nucleus like planets around the Sun — that model, while useful for beginners, is fundamentally wrong. Electrons do not follow neat circular paths. Instead, quantum mechanics tells us that an electron exists as a probability cloud, and an orbital is the mathematical description of where that cloud is densest. Think of it like a firefly in a dark room: you cannot predict exactly where it will flash next, but over time you would see it lights up certain regions far more often than others. That glowing pattern is the orbital.
Orbitals come in distinct shapes labeled s, p, d, and f. An s orbital is spherical — a fuzzy ball centered on the nucleus. p orbitals look like dumbbells or figure-eights, with the nucleus at the pinch point, and they come in sets of three oriented along the x, y, and z axes. d orbitals are more complex, with cloverleaf and donut shapes, appearing in sets of five. f orbitals are even more intricate, with seven orientations. Each orbital can hold a maximum of two electrons (with opposite spins), so the s subshell holds 2, p holds 6, d holds 10, and f holds 14 electrons.
Understanding orbitals is the key to understanding all of chemistry. The shape and energy of orbitals determine how atoms bond, why molecules have specific geometries, and why the periodic table is structured the way it is. The reason period 2 has eight elements? Because it fills one s orbital (2 electrons) and three p orbitals (6 electrons). The transition metals exist because period 4 starts filling d orbitals. Even the colors of gemstones and fireworks come down to electrons jumping between orbitals and releasing photons of specific energies.