I'm guessing you mean "directed energy" weapons, which are something you'd aim at a specific target, rather than just generic "energy" weapons like bombs, nuclear devices, and EMPs.
A directed-energy weapon, as the name implies, directs energy in a particular direction by a means other than a projectile. Put another way, it transfers energy to a target for a desired effect.
Various types of these weapons exist or are in the works. They fall into two broad categories: Electromagnetic radiation (light, microwaves, etc.) and Mass weapons (particle beams, etc.).
Visible light can be used as a directed-energy weapon. Bright searchlights can be used to blind, strobing pulses of light can be used to induce extreme vertigo, for example. Heck, a good mirror array on a sunny day would be an excellent directed-energy weapon.
Laser weapons do exist in real life, such as the Tactical High Energy Laser and the airborne laser system, which are used to shoot down airplanes and missiles.
Lasers can be used to blind, of course. They also have great potential as weapons, as they can deliver enormous amounts of destructive energy to a precise location. The difficulty at present is the fact that weapons-grade lasers generate so much energy that they need to be constructed carefully enough that they don't destroy their own innards first. It's definitely doable, though.
It's also tough to transmit a weapons-grade laser through the air without turning the surrounding air into a plasma in the process. Super-short bursts of energy minimize this problem, as does focusing several smaller beams of energy that won't burn the air onto the same point. But those aren't always practical solutions.
This can be turned into an advantage, however. Some weapons systems currently in development use a laser to burn a plasma path to the target through the air. Then a powerful electric charge is sent down that plasma path, like a bolt of lightning. Imagine a Taser on steroids.
Another problem with lasers is that they burn off the surface of the target first (obviously). This tends to create a cloud of ash that blocks the laser from continuing to get through. This limits their effectiveness for certain kinds of targets.
The biggest problem with lasers is that, to deliver a weapons-grade burst of energy, you need to supply all that energy. We're talking megajoules per burst here. It's doable though, especially with sufficient electrical supply. Which is great because it's easier to transport than tons of solid ammunition and explosives.
Microwave lasers are great, because they destroy electronics, and can be used to cook the target. Just like a microwave oven, just targeted. These are also useful for crowd control and non-lethal enemy incapacitation, by raising skin temperature to unbearable horrible screaming temperatures without causing internal damage.
Particle weapons are also very cool:
Electrons leap to mind first, of course, as we're all used to electricity. The directed lightning along a laser-induced plasma channel was mentioned above. And electrical discharges can be sent short distances with great effect. But to get any long-distance discharge without a plasma channel, you need to operate the weapon in the relative vacuum of outer space. Where it's hard to focus.
What about this plasma we keep mentioning? It's essentially a bunch of supercharged particles. Could be very useful. In fact, we do use plasma torches for cutting metal -- essentially a high-voltage arc creates a plasma from the air, which is then blasted out at high speed. These are self-focusing, forming a cone of cutting plasma. At present, these can be used to cut through about 30 cm of steel in one go, but it's conceivable that this technology can evolve to the point where directed bursts of plasma are propelled over larger distances. Not expensive, and not all that heavy either.
There's tons more information on this stuff all over the internet, I'm sure.
