Naming variables:

Local variables (variables inside and only applying to one function, statement, or loop) always begin lower-case, and any new words in the name are capitalized.

examples:
price
totalPrice
gayAsianPornRightHereBro

Global variables (variables declared outside of functions that can be used throughout the code and aren't specific to any function, statement, loop, etc.) always begin capitalized and any new words in the name are also capitalized.
Tax
Income
TotalIncome
Pi
AndrewsAFagBag //Hurrrrrrrrrrrrrrrrrrrrrrrrrrr

Member variables (variables declared inside classes/structs) always begin with an underscore and a lowercase letter and new words in the name are capitalized.

_memberName
_price
_id
_praiseAllah