Project #3:Can't understand the formula

I've read an earlier post(more than 120 days ago) about the same issue of understanding the formulas used to calculate the TMP36 measurements of Volts and C degrees.

TMP36 measuring a range from -40C up to +125C.
Analog input translating it to a number between 0 up to 1023.
How the formula is working?

Why to find the voltage i need to multiply with 5? because of the supply voltage?

There is another formula than can be used here to convert the voltage to temperature? I'm asking because it's seems to be working only for 25C or this how it should be done?

Sorry for my bad English grammar.
Thanks for the help.

Probably a better explanation HERE

It explains how the temperature is proportional to the voltage.

And that once you have the voltage mapped you can then use that number to obtain a temperature.