What can be said about the stairs?

Windows in houses today should perform the function of isolation from external conditions. Basically, plastic windows and attic are used. Depending on the constructive purpose, climatic conditions and aesthetic qualities, the windows are made of the following materials: fiberglass (has good strength and resistance to high temperatures), wood (has good environmental friendliness, less sensitive to heating and can undergo secondary processing by more than 90%) , aluminum (has high strength and is able to withstand heavy loads and pressure when installing facade windows). What can be said about the stairs? Due to the difference in height in the house, there is a need to install a stairs. It allows people to move from one level to another.