The brain can carry out several tasks at the same time because it splits a larger task - playing tennis for example - into smaller ones: seeing, hearing, moving, etc.. One part of the brain analyzes movements of the tennis ball that we see, while another part actually recognizes the ball.
Our brain consists of several parts. These parts include the brainstem, cerebrum, hippocampus. Maybe you have heard of them before.
In order to read this sentence, you are now using the cerebrum in your brain. And if you remember the information on this page, it has been stored in your hippocampus which houses the memory.
In addition to all the different brain-parts there is the functional unit of the brain: called a neuron. Neurons convey information using signals. There are approximately 100 billion neurons in the human brain. Each of these neurons will have more than a 1,000 connections to other neurons.