Modern computer chips handle data at the mind-blowing rate of some 10^13 bits per second. Neurons, by comparison, fire at a rate of around 100 times per second or so. And yet the brain outperforms the best computers in numerous tasks.
One reason for this is way computations take place. In computers, calculations occur in strict pipelines, one at a time.
In the brain, however, many calculations take place at once. Each neuron communicates with up to 1000 other neurons at any one time. And since the brain consists of billions neurons, the potential for parallel calculating is clearly huge.