When we use i.e., and e.g., and what do they mean?

Answer: The Latin abbreviations "i.e." and "e.g." come up very frequently in writing and would probably come up more often if people were more sure of when it is right to use "i.e." and when "e.g." is required. To me, the only way to figure it out is to know what they stand for.
i.e.

"I.e." stands simply for "that is," which written out fully in Latin is 'id est'. "I.e." is used in place of "in other words," or "it/that is." It specifies or makes more clear.
e.g.

"E.g." means "for example" and comes from the Latin expression exempli gratia, "for the sake of an example," with the noun exemplum in the genitive (possessive case) to go with gratia in the ablative (prepositional case). "E.g." is used in expressions similar to "including," when you are not intending to list everything that is being discussed.