pirojki (singular form is "pirojok") are small pies with different fillings (meat, cabbage, jam etc.) they are either fried in oil or baked. chebureki (sing. cheburek) are borrowed by the Russians from Caucasian cuisine. A cheburek is a kind of a pie. It is slightly larger and flatter than a pie. Besides only meat can be its filling and it is always fried in oil.
Chebureki and pirojki are very popular with the Russians. They can be found in any canteen or snack-cafe. They are very tasty too!))