Oktoberfest is a festival that started in Germany.. tons of german cuisine and lots of beer, music, dancing etc. Various cities around the world have their own version of Oktoberfest around the time of the actual festival (Kitchener's is much shorter than the original one). The reason Kitchener has it is because when it originally became a town it was called Berlin and was largely made up of German people. It became a tradition.
I'm like 90% sure about all of that, so please don't verbally rape me about technicalities lol.