This is a great question, with a complex answer. First, we have to define what a robot is.

Typically, we think of robots as machines which can automatically carry out a complex set of actions. We usually think of these machines as being computers which are programmed by humans. However, there are a variety of materials which can act as "robots" in the sense that they can be "programmed" to perform actions such as "walking."

For this question though, let's just think about the robots we define as computers which are programmed by humans. A lot goes into designing robots that can walk. Here are a few things to think about. One of the most basic things needed is to write a computer program which will instruct the robot to respond to its environment appropriately under different conditions. For instance, what should the robot do if it encounters a wall or another obstacle? What about stairs? The robot will also need some way to get information about its environment in order to make these kinds of choices. Thus, the robot must be build with materials which can transmit some kind of signal to process information. The robot must also be built in a way that is stable enough for it to walk and not fall over as it moves forward on its own, or if it accidentally bumps into something. It will also need a source of power (a battery) to do any of these tasks. These are just some of the considerations that go into making robots that can walk. I hope this helps!