The distinction between the two terms is primarily that organic compounds contain carbon, while almost all inorganic compounds do not. There are, however, some inorganic compounds that still contain carbon, such as carbon dioxide. Almost all organic compounds contain carbon-hydrogen bonds, and, as of 2014, some scientists have recommended that this requirement be included in the definition of organic compounds.
Sciences360 explains that this distinction is not a formal scientific classification but rather just a useful categorization of carbon-based compounds. Molecules that make up the parts of living things, the building blocks of life, such as proteins, fats, sugars and enzymes, are considered organic molecules. These complex organic compounds are based on carbon because it has the unique ability among the elements to form up to four different covalent bonds per atom and essentially bond with other carbon atoms indefinitely. This property allows it to form compounds with an almost limitless variety in structure.
Another distinction is that, when compared with organic compounds, inorganic molecules are often far simpler in their composition. Table salt, for example, is an inorganic compound made up of one sodium and one chlorine atom, while one of the most complex organic molecules is human DNA, a compound that can be thousands of atoms long.