A mixture is a substance made up of two or more substances that are not chemically bonded e.g. air.
Compound
A compound is a material made up of two or more components that are chemically bonded e.g water.
Air as a Mixture:
Air is a mixture, and not a compound because air can be separated into different components such as oxygen, nitrogen, etc. through the process of fractional distillation.
Also, air shows all the properties of gases present in it.
Air consists of mixtures of gases, hence, it is a mixture.