Horatio's position in Hamlet?

when they say things like "I am your servant" or here "your poor servant ever", it's just an expression. it's like saying "I'm at your disposal" or "I'm always here to help." he doesn't mean he's literally his servant, but that he's always available to come to Hamlet's aid. and I agree with the first answerer, that he says "my lord" just because Hamlet is a prince.