When people think of robots they normally imagine a two-legged humanoid robot, similar in appearance to a human being.  Something that can walk in a similar fashion to a human (although in the past they walked with very stiff jerky movements), something that can carry out some form of communication with people and perform given tasks.  Humanoids are seen as our servants, friends and companions.  This type of robot is sometimes classified as an "android".  Many films a TV programs have  characterized this form. Lost in space, Star Trek, Aliens and Red Dwarf to name a few.

Why build humanoids?
    People tend to like humanoids, they can relate to them.  This does have limits though, the Honda P3 humanoid stood at over 6 ft tall and was very heavy, some found this to be a little intimidating.  The P3 was replaced with a smaller version.  There is also a theory that to understand intelligence in something you must study that intelligence from its own actual form or embodiment.  In other words if we are to understand human intelligence we need to start by creating a human form and then have this form interact with the world in which we all live.  It is then hoped that we will begin to see how our own intelligence formed.
    Robot comes from the Cechozalian for slave or worker.  This is what we wish for from our humanoids friends, a robot in the home that can carry out the tasks we give: feed the dog; do the ironing; post this letter.  There is a theory that if you want to imitate the actions of another, say copy what a human does - feed the dog, you need to have similar phyisical appearance to achieve this.  So in theory it is going to easier for us to create robots that can do the tasks we want if they have a smiliar phyisical appearance - two arms, two legs etc.