Formal generally means following explicit or implicit rules in behaviors. Informal is just the opposite of formal. Being professional is considered formal.

formal is the cinema and informal is a gay man

what is formal and informal communication

formal is just study of logic with purely formal content and material is the branch of logic that focuses the content of reasoning.

A formal organisational structure a formal structure exists where there is a recognizable chain of command and a formal communication software Informal Organisation Strucutre An informal organisational structure is more relaxed; networking and informal communications with members of staff