that's a terrible definition... start doing research online... it's fairly simple in how it works... but it takes pictures and stuff to fully understand

http://asia.vtec.net/spfeature/vtecimpl/vtec1.html

http://www.teamdelsol.com/technical/techstuff/vtec/

http://www.leecao.com/honda/vtec/whatsvtec.html

those 3 pages go into way more depth and they will help your better understand it all. read.love.know