Hi, if post #2 is just too clear, concise and correct to be helpful, apparently, TI have a great set of online tutorials and exercises for people who want to learn about op amps - and while there, why not check out all their endless selection of op amp resources!
Put a fast signal through a slower op amp and the output signal will be horrible and may miss subsequent input signals because it is too slow to keep up, like me in general in life or like a machine on a production line that is slower than the products on the conveyor belt passing it so only half the bottles of lemonade will get a cap on them - the machine is too slow to see bottles 2, 3, 4, 5 and only puts a lid on again at bottle #6.