This video introduces biological molecules by first establishing a foundation in organic chemistry. It explains that organic chemistry focuses on carbon-based compounds and their structures, which are essential for understanding biological molecules. The video then defines hydrocarbons as organic molecules composed solely of carbon and hydrogen, linked by non-polar covalent bonds, and discusses their non-polar and uncharged characteristics, making them hydrophobic. The presenter also previews the next video, which will cover functional groups that can be attached to hydrocarbons, influencing their properties.