Autofill is used to fill a particular function throughout all the rows.
Eg. If youve written price of Audi car in one cell B1 and price of Alto car in B2
In the other column you've written the number of Audi cars in cell C1 and number of Alto car in cellC2
Q : you have to write the total Amount of all cars of a particular brand.
In cell D1 you write the function: B1*C1 press auto fill and will get the function replicated in the next row giving you the correct answer