The observable properties of star clusters hold vital information concerning the star formation process. In this introductory chapter we review the properties of open clusters within the Galaxy. Starting with the most basic properties of open clusters, such as age, mass and metallicity, we then move onto a discussion of how these properties vary depending on the number density, cluster mass and spatial distribution across the Galaxy. In addition to these observables, we also describe methods of selecting members of open clusters through the use of proper motion and radial velocity kinematic information, and demonstrate their usage in highlighting dynamical evolutionary processes, for example, mass segregation. Finally, we end this chapter with a discussion of unbound stellar populations, namely OB associations, and their relation to molecular clouds within the Galaxy.