Your way of behaving or acting is your manner. Your parents might be fooled by your best friend's quiet, polite manner, but you know that she's capable of being incredibly rude — and hysterically funny.
A manner is also a style of doing something. You may not like the manner in which your boss at the coffee shop does things, but you have to admit she makes a perfect latte. Manner also means the kind or sort. If you find yourself working with people who enjoy stabbing each other in the back, you may wonder what manner of people you are working with.