[Python] What does "e" in "1e-5" in Python language mean and what is the name of this...

I notice that there is such an expression "1e-5" in Python(probably in other languages also)

1. 
   What is the name of this notation?
   
   
2. 
   what does it denote in math?
   
   
3. 
   What does 'e' mean? It's the first time I see a character helps to denote some value, are there other characters also help do so?
   
   
4. 
   Why should use this way instead of some other python math operation like pow() etc.
   

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