The word balcony refers to several definitions, but each of design has similarity. In residential housing, you will find this part as extended section attached at the second floor. It has a part of upper where homeowner can step outside as terrace. You can call it as terrace for the above floor. This implementation is applied for apartment and building. Any extended part that resembles terrace or porch will be called as balcony.
Several factors lead builders or architects to add this part in their building. At home, you can enjoy the fresh air from second floor or look at beautiful view directly toward surrounding. This is common function that applies also to the apartment and building. It is like outdoor section in apartment, but attached on the wall directly. For building, it depends on purpose and functionality. The office is rare with balcony due to security and safety situation. On the other side, building with extended part at outdoor is mostly for specific function. For example, it is a church where priest gives blessing and preach.
Besides outdoor area, balcony is also capable to build in indoor position. You might be familiar with theater that uses this part as the stage or for viewers. If the stage is at low floor, people can see it from the top directly with balcony. That’s why this part attaches on the wall from indoor area. On the other side, it is useful as the stage itself during performance. Music concert mostly rely on higher ground area to make sure everyone can watch. It is another practical function for this part.
In apartment, balcony acts as the yard and you can decorate it with proper furniture. If you like gardening, this is where you put the pots or boxes for flowers and plants. This is common idea in urban area where the land is limited, but may need the outdoor section.