Extracted from (here), multitasking is can mean performing two or more tasks simultaneously, or it can also involve switching back and forth from one thing to another. Multitasking can also involve performing a number of tasks in rapid succession.
Some researches shows that multitasking is wasting a lot time and reduce productivity. You dont have to agree with that.
I am blessed with the ability of multitasking and I know it is necessary most of time if you are a wife, a mother with 4 kids, no maid and you are working, involved in international negotiation, organising a charity event, running your own businesses and prepare entries for numbers of competitions, all at the same time. But you dont have to do it all the times. For me, multitasking is fine.