Whether the brain is a computer depends on how you define "computer" and perhaps also "brain".
No, it really doesn't.
The human brain is a reflex engine. It reacts to stimuli in various ways. One of those ways is to produce external behaviors in the body it's attached to, the other is to slightly alter its own structure in response to those stimuli. The brain's response to stimuli depends
entirely on its physical structure at any given moment. Because each new stimulus produces a slight change in that structure, it never responds to the same stimulus exactly the same way. This is the main reason why training and education are required for human beings: the goal is to bombard the trainee with repeated stimuli of the same type which the trainee then attempts to respond to with a specific action. Over time, the structure of the brain forms in such a way that a specific set of stimuli is more likely to produce a specific set of desirable behaviors. This takes a long time to do, and does not always work very well.
Computers, on the other hand, operate by consistent logical rules. The most basic of these rules is the mathematical distinction between 1 and 0, which map to "true" and "false." This is the limit to what a computer can actually process: a bewilderingly huge number of "true/false" statements across a physical array of several billion transistors. Computer's process information by combining these many true/false statements in all of its many logic gates, and you can, in essence, describe literally ANYTHING if you have enough true/false statements in a table (the Turing Machine).
What a computer does when you feed it an input depends on the state of its true/false values in its memory. It is analogous to the human brain ONLY insofar as how and when inputs alter the true/false value of those transistors depends on how its memory has been arranged in the first place (e.g. "11001001" is a read command and "00110110" is a write command.) The similarities end there: computer memory is a set of data introduced to the processor through logical processes, where human memory is a set of reactions introduced to the brain through stimuli. Strictly speaking, the brain is more similar to a ball of clay than a computer: if you press your hand against the brain, it'll leave an impression that degrades over time and never actually becomes permanent; if you press your hand against the computer, it'll record a "1" at all the places where your skin touches and a "zero" everywhere else.
The ability to take in, retain, and comprehend information. Comprehension involves the ability to recognize patterns and meaning in that information and extrapolate those patterns to make accurate predictions about the future or about unknowns. For example:
- Look at a sequence of numbers, figure out the pattern, and find the next five numbers in the sequence
- Look at an object that is partially concealed by another object, and find a way to manipulate the second object so that the first is no longer obscured
- Given a description of person A and her behavior, and a set of circumstances that happen to person A, how does this person feel?
- Write a sentence in the passive voice
- Write a sentence in the active voice
- Estimate the volume of an oddly-shaped object
These are all different "types" of intelligence but they all depend on the same thing: the ability to recognize patterns, and extrapolate those patterns to predict the future.
Human beings gain the ability to recognize patterns by being exposed to those patterns repeatedly in their lives. You see the same thing over and over again, you learn to recognize it the next time you see it. When you see the same thing with slight variations over and over again, you get better at seeing through the slight differences and recognize what's important about it. Sometimes, a new variation throws you off and you have to stop and think "does this still fit the pattern?" and maybe it does, maybe it doesn't, and you have to decide if it's part of the same pattern, or something new, or something in common with another pattern. This is one of the reasons intelligent people are better at dealing with ambiguity than others.
Machine intelligence is similar to humans in that it collects data on certain patterns and finds ways to extrapolate that pattern to predict the future. Computers cannot natively learn to recognize patterns, however, and are totally dependent on software and pre-programming to be able to do this. This limits computer intelligence to the extent of its existing knowledge base and its ability to extract meaningful patterns from that knowledge base.
What about animals? Are animals intelligent?
At certain things, yes. Some of them, VERY. The ability to predict whether or not a predator is going to notice you and/or eat you or fail to notice you and walk on past is an important survival skill for most animals. For predators, the ability to judge distance, determine where a tasty animal is and where it's going, figure out how to catch it and how to kill it, are equally essential.
Are there animals that are more intelligent than other animals? Do you think an animal species will one day, after countless generations of evolution, gain the "Superintelligence" that proponents of technology singularity claim machines will ultimately gain?
No, because "superintelligence" or even humanlike intelligence are not necessarily advantageous from an evolutionary standpoint. Humans are very good at learning how to do things we usually suck at, which makes is accomplished generalists at a time when being a generalist is an advantageous trait. Other species haven't had the time to evolve generalist traits -- YET -- and we simply got here first.
