Think of it this way, when we walk we push the ground backward with our feet,
But we cannot move the ground,
So what happens?
When we push back on the ground our feet does not move backwards but we are applying a force so that means that there must be an equal and opposite force..................................and that force is friction.
It could be better explained with a free body diagram but i cannot post images so you may try to make it yourself
 
So since your feet are not moving you can sort of anchor one of your foot on the ground and propel the rest of the body forward by using your muscles and if you think about it this is the exact rerason why you cannot walk on ice. Since the friction between your feet and ice is very less the anchoring force provided by the friction is very less so you cannot anchor your feet ont the ground  and cannot anchor your feet on the ground
 
 
Now the next part of your question i cannot answer in a article without the capability to addf images and i cannot post an external url so i cannot really help you there