Meeting invent help company this week to sign a confidentiality agreement pertaining to idea is that legal binding?

A decent confidentiality agreement will keep the associated disclosure from being a "public disclosure" and therefore giving up your international rights and starting the 1 year deadline to lose your rights in the US. As to how legally binding any particular agreement is and how well it can keep someone from stealing your idea, that comes down to the specific terms of the agreement and who is involved. Generally, you will need to consult with an attorney to get an idea about how much a particular agreement protects you.