HCl can exists in two forms. It is either in aqueous or in gaseous form. It can be formed from Hydrogen and chlorine ions or gasses. 

Hydrogen Chloride aqueous delta H f = -92.30

Hydrogen Chloride gaseous delta H f = -167.2

examples of production of HCl

Aqueous HCl can be produced in our stomach from Carbon dioxide and Water as starting material.

CO2 + H2O ---> H2CO3

carbonic acid produces proton

H2CO3 <---> H+  +  HCO3-

That can combine with the freely floating Cl- ion in the cell thus producing HCl.

Gaseous HCl can be produced via burner process. This is an exothermic reaction.

H2 (gas) + Cl2 (gas) --> HCl (gas)