“Liquid smoke” will bring a smokey flavour to your dishes.
Practically it is made of steams coming from burning woods like hickory. It is quite controversial as some brands add chemical additives that have had a carcinogenic reputation. Some other brands like the one in the picture do not use any but have aged the steams in oak barrels just like whisky, ending up in a more expensive but naturally flavoured smoke!
Check that labels do not contain any PAHs (polycyclic aromatic hydrocarbons).
Famous in the United States, it is not so much in Europe and have been controlled by the European Union.