Mr (Mister) is used before a surname e.g. Mr Jones or a full name e.g. Mr Tom Jones
Messrs is the plural of Mr and is used in business English for company names e.g. Messrs White and Brown
Ms /miz/is used when we don't know if a woman is married or not. This is the most commonly used title today.
Mrs is used before a surname for married women e.g. Mrs Jones or before a full name e.g. Mrs Angelina Jones
Miss is used for unmarried women. e.g. Miss Jones
Doctor/Dr if they are a medical doctor or have a doctorate degree e.g. Dr Jones