Any chemical that dissociates to give an H+ ion is classified as an acid. There are stong and weak acids but at GCSE you only need to know some key reactions which apply to both weak and strong acids.
acid + metal = salt of the acid + H2 gas.
acid + base = salt of acid + H2O
acid + carbonate = CO2 + H2O + salt of acid
Each time the salt of the acid is named as follows:
If the acid is HCl the compound will be a metal chloride,
If the acid is H2SO4 the salt will be a metal suphate
Similarly, if the acid is ethanoic or methanoic acid, the salt will be an ethanoate or a methanoate respectively.
eg. ethanoic acid + potassium hydroxide = potassium ethanoate + water