whats the difference between float and double?

Answer 1

Float - length 4 bytes - numbers until 10^38 - example 10.0f, 12.5f
Double - length 8 bytes - numbers until 10^308 - example 10.0, 12.33

Answer 2

At first you are welcome to use an internet search engine for this problem. There is a bunch of easy to get information out there. The basics are written down on places like this: https://msdn.microsoft.com/en-us/library/1dhd7f2x.aspx

For further questions or if you don't get it feel free to ask me again. Will See how I can help you.