Inclusive design is design that considers the full range of human diversity with respect to ability, language, culture, gender, age and other forms of human difference. Designing inclusively results in better experiences for everyone.
You or anyone can think inclusively by just trying to view the world in the perspective of others and think about how the daily lives of someone could be changed due to a difference that they may have from others.
Everyone should think inclusively because as a society everyone is equal and everyone should be included and taken into consideration. When we think inclusively we will see the disadvantages of someone living with some form of human difference, so we can try and address that issue through designing.
Universal 
design and inclusive design are very similar and sometimes one may get confused with the other. Universal design is design that is used by most people but often segregates the others that aren't capable of using it. Inclusive design addresses this issue because it includes everyone and it is focused on every individual which results in a more reliable and better design than universal design.
Inclusive Design is built for and would appeal to everyone, where regular design would only work for the majority, while leaving out a large margin of people unaccounted for.
Of course! Inclusive Design includes and applies to everyone, regardless of age, race, or anything that makes us different.
One example of something that is inclusively designed is modern architecture, in the sense that it is very hard to build a public building constructed without building elevators (for people who can’t take the stairs), braille signs (for people who are unable to read/see regular signs) and automatic door openers (for people who are unable to open doors on their own).