The Vigenère Cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword - Wikipedia.
Please read the article on Caesar Ciphers if you haven't already because the Vigenère Cipher is a direct derivative of the former. The Vigenère cipher takes a keyword and applies a certain caeser cipher to it multiple times according to the letters of a keyword.
Vigenère Ciphers appear to be identical to any other substitution cipher, but trying to solve it as Caesar Cipher will not work. Check for this type of cipher if the Caesar Cipher crack does not work.
DEKTHON 2014 had a simple vigenère cipher with no hints and only a line of text:
Solution can be found here.