what are indentifiers

Answer 1

Depends on the context. E.g. unique (in an environment) codes (numbers. text, adress) that represents something uniquely.

Examples:

The set (Name, Birthday, Birthplace) is a identifier for people, VINS for Cars (in a timeframe of aproximately 20 years), GUID's are text based identifier for what ever, MAC adresses are unique for network cards, an IP represents an network device, an URI a web resource and so on ...

Answer 2

Identifier is a name given to a variable/function/any element of your program.
For example in: int num = 10; "num" is an identifier of the variable of type int.
It should be unique for the scope it is used in, follow the naming rules (I think they are taught in the C course) and not use any reserved keywords.

Answer 3

Its a name give to a variable

Answer 4

That's the programming context. Thx.