Release Profiles:
- predefined customizable profiles different configs that allow programmer to have more control over various options for compileing code
- dev profile cargo uses when run carbo build release -- relase 
- opt-leve setting controls the nubmer of optsimizationss Rust will apply to your code range 0 3
- //two slashes, documentation comment
- generate html documenation 
- documentation comment use three slashes, instead of two and support Markdown 
- examples markdonw panics: scenarious in which the function panic, 
- errors Result kind of errors that might occur
- safety unsafe  why the function is unsafe and covering the invariants that the function exepects callers uphold
- description and licesne info are required