what does e mean

Lets use an example of e:

 

One Quadrillion. It is represented as 1.0e15

Because ^^^ has 15 zeros in it. (1,000,000,000,000,000 = One Quadrillion)

So you do 1.0e(How many zeros are in the number) for extra long number.

Also like googol. It is represented as 1.0e100 because googol has 100 zeros in it.