I use runes and sigils all the time. Grim-reaperT is right. They are pictures or drawings like squiggly lines that form some type of image. They are primarlly used in defensive magic like wards. But they can be used in anything.
Sigils are symbols that can mean different things and used for magickal purposes. Generally, most are made of letters from words, but there's no real guidelines. When you make them, you just do what you feel makes it right.
It's a sign or a sequence of letters. Used for meditating about the enitity you want to evocate aka charging the sigil.By a sigil you by pass the conscious mind and you put it inside your unconscious mind.(an example are subliminal messages).