Question about star wars episode 4? Please only ppl who have wacthed and really konws star wars?

Ok so My husband Love star wars and got me to wacth them. I am really really lost now. On the 4 one a new hope. The 2 robots are they the same from the other moives if so why don't anyone know them? Why don't they kow anyone? Please explain this tio me. My husband caan't