What is the meaning of Aluminium_chloride?

AlCl, only exists in the gas phase when AlCl3 is heated with aluminium.

AlCl3, the aluminium salt of hydrochloric acid; forms the covalent dimer Al2Cl6 when melted; it has very many industrial applications, including that of a catalyst in Friedel-Crafts reactions.

Source: wiktionary.org