Simply, computers are those electronic devices which can compute calculations upon giving a particular arithmetic or logical operation automatically. Computers in general are dumb, because it doesn't not have intelligence of its own. Each time, computer is given a command to perform a given calculation or operation.

But as  time advanced, computer programs too advanced. 

Now a days, some of the computers are smart too. I said some because some computers are equipped with softwares like artificial intelligence. These softwares are so good that it can function on its own just by giving on some of the commands. Some intelligent robots can sense their environment by their sensors and anomalies and function according to it.