Multi tasking can be defined as the ability to do many things in a given time frame.
So it is an art and a difficult one at that. In fact most people cannot multi task and hence lose out on efficiency. Even students are known to multi task while studying. Most children use laptops and move from screen to screen with unrelated topics in each.
Even relaxing involves multi tasking these days. Many Americans are known to be chatting online or over phone while watching TV. Smart phones have made multi tasking even more compulsive.
Multi tasking lowers IQ, lowers efficiency, loss of time and a difficult habit to kick. In short, multi tasking confuses your brain and slows you down.