What is the difference between terraced house and semi-detached house please?

A flat is a dwelling with more than one occupant in a block or building,a terrace is a house which can be at the end of a row of houses or it can be sand which on either side,a semi- detach is only attach on one side of a house,a bungalow where all the rooms are on the ground floor no stairs,a cottage is a small house in the country.