What is the difference between data types &identifiers?

Answer 1

The identifier is the variable's name: must start with a letter or an underscore(_) , and you can choose any name you want but it is better to choose a descriptive name
And data type is the type of the data ( like int, str..)

Answer 2

data type is which you want identifier type. if you want int type identifier you must declare the int of you want identifire or veriable name... same as type of veriabale....