'Condo' is short for condominium. A condominium is an apartment that you own. The condo would be part of a building containing other condominiums, each owned by the people living in them. The main building and grounds would be owned by a single person or organization. In summary, you rent an apartment, you own a condominium. Also, a single house would NOT be a condominium.

Thank you;After the new year of China,I think I would be very lucky to be your student

An apartment is a house or a place that you only rent. You can never own it. It may be a house or a flat in a building. Meanwhile condo is a place that you own in a building. It should be in a building, otherwise you call it a house.