Light sabers use a fictional energy source called kyber crystals to power a plasma blade. The blade is contained within a magnetic field and can be extended or retracted at will by the user.
As of now, light sabers are not possible in real life. The technology to create a contained plasma blade and a power source small enough to fit in a handle does not currently exist.
The temperature of a light saber's blade can reach up to 27,700 degrees Celsius, which is hotter than the surface of the sun. However, the magnetic field containing the blade prevents it from burning the user's hand.
In the movies, light sabers are shown cutting through almost anything, including metal and other lightsabers. However, in real life, it would depend on the strength and composition of the material. A light saber would likely have difficulty cutting through dense materials like steel.
There have been attempts to create light saber replicas for use in fencing and other sports, but they are not widely used or recognized as legitimate equipment. Additionally, the safety concerns and regulations surrounding the use of a high-temperature plasma blade make it unlikely to become a mainstream sport weapon.