When a statement has many examples it is correct to use "e.g.," which is an abbreviation of _exempli gratia_, which in turn is Latin for "for example." For example: There are many emotions a person may feel, e.g., happiness.
When a statement has only one logical conclusion it is correct to use "i.e.," which is the abbreviation of _id est_ which in turn is Latin for "that is." For example: It was the same colour as a clear summer's day sky, i.e., blue.
When a statement has many examples it is correct to use "e.g.," which is an abbreviation of _exempli gratia_, which in turn is Latin for "for example." For example: There are many emotions a person may feel, e.g., happiness.
When a statement has only one logical conclusion it is correct to use "i.e.," which is the abbreviation of _id est_ which in turn is Latin for "that is." For example: It was the same colour as a clear summer's day sky, i.e., blue.