What is difference between css and css3

● What are the selector in css

● What is media query in css

● What is different position in css

● What is bom in css

● What is difference between PX,unit,em,rem in

css

● What is flex box in css

● What is pseudo selector in css

● How to make website responsive

● What are breakpoint for viewport responsive

device

● Why we use box-sizing in css