In English-language recipes, fond usually means the browned food deposits adhering to a pan after searing or roasting. Dissolving them with liquid by deglazing adds depth to a pan sauce. Brown deposits are desirable; blackened, bitter residue is not.
French culinary usage also includes stocks and sauce bases under fonds. The browned deposits themselves may be called sucs. Fond is unrelated to fondant icing or fondue.
Reference: Further reading.