Dipole. This is a little more complex sort of antenna, and they’re everywhere. The most common way of thinking about a dipole is a “rabbit ears” antenna but really most indoor antennas, whether they are cats’s whiskers, bowties, loops or flat squares are all dipoles.
If you look at a pair of rabbit ears, you’ll see that they look like two monopoles. That’s essentially because they are. However, they’re able to do more than a monopole because of the way a dipole antenna connects to the receiving circuitry. In a monopole antenna, the antenna itself connects to the “signal” part of the cable while the “ground” part of the antenna connects to something else. In a dipole, each of the two elements connects to the cable. This gives the dipole quite a bit more receiving power than the monopole. Both sides of the dipole can be aimed independently although the ideal setup has both sides pointing away from each other.
The dipole antenna is more effective at picking up specific frequencies and can be combined into a complex array (something for another article) if needed. It’s also the oldest form of antenna, actually having been invented before the monopole. It’s very specific in the way that it’s best used, and the mathematical formulas that govern its use are really, really complex, which is kind of funny when you realize that most of us use dipoles by wildly flailing the elements in weird directions until something looks good.