The Sidhe are a proud magical race of elven people. They basically are the top of the upper crust. The Sidhe classify themselves into two Courts: Seelie and Unseelie. The Seelie are sometimes seen as the good guys and the Unseelie as the bad guys. Although both can be seen as good or bad depending on what aspect is being looked at. The Seelie and the Unseelie have an ever present hatred for each other. The Seelie considering the Unseelie as wild and uncivilized. The Unseelie seeing the Seelie as arrogant and oppressive.
The Sidhe as a whole are beautiful people, and know it. They are not above using that beauty to get what they want.
As far as powers go, there are three powers that ALL Sidhe have in common: Glamour, the Touch, and Teleportation. Teleportation, obviously, is simple teleporting from one location to another. Of course the more experienced you are, the better you can teleport. Those who have just learned, will have difficulty teleporting outside the building they are in. Those who have been around a while and know the full extent of their powers, may very well be able to teleport to the other side of the planet. To teleport somewhere, it must be a place they have seen before. Whether it is with their own eyes, in a picture, or even in a mental image, such as through the the Touch.
The Touch, is a conscious release of magical energy through physical contact. Physical contact, holding hands, touching a shoulder, any kind of touch, is not always the Touch. It must be a conscious release of energy, willingly giving that energy to the person they are in contact with. This release of energy is pleasurable for the one receiving it. All magical beings can recieve the Touch, but only Sidhe can give it. The Touch must be through actual skin to skin contact. Thoughts and emotions are often transferred along with magic during the Touch, but the pathway is one way. Always going from the Sidhe to the one being Touched.
Now Glamour, is fairly simple. All Sidhe are elves. They posses elfin traits, like the slight points to their ears which would be obvious to anyone who saw them without some form of disguise. Glamour is the disguise used by most fey. It is our way of altering our appearance so that we fit in with the locals more easily.
The final point about all Sidhe is that every individual has a unique power that pertains only to them. Although there is no limitations to what that power might be, those who are Seelie lean more towards powers of Light. Where as Unseelie lean more towards powers of Darkness.