Focus on Multitasking

My English is not very good but aren't focus and multi-task are two opposite mentality? When you are focus, you are concentrated on a particular task at hand. When you are multitasking, you are doing many things at once. So how do you focus on multitasking? When I heard people said this, I am confused. You can't focus when you are distracted by millions of other things. You could argue that focus a little bit on each task but your focus is divided up in portions, you are not focused anymore. Next time, for those of you who said this before... don't say that anymore. It doesn't work! Either focus OR multitask, not both.