What is the difference between a 'formal invitation' and an 'informal invitation'?

What is the difference between a 'formal invitation' and an 'informal invitation'?

Charlie Scola (Event Planner, Charlie Scola Catering) gives expert video advice on: What is an 'invitation'?; What should I consider when choosing invitations?; What is a 'save the date' notice? and more...

The difference between a formal invitation and just a regular invitation is generally the style. A formal invitation will usually have a response card inside, whereas an informal invitation will not. It's just an announcement.