When you are the "Section Leader" of a group (CMP, MXE, PXE, MSP), you can add people to your Qwire project as "Members".
"Assign Member" is used when a user already has registered to the Qwire Gateway. They will get a link and next time they log into the Gateway, they'll see the Project.
"Invite Member" is for a user that has not registered on the Gateway. They will get an "Invitation Code". They then can register on the Gateway, select "Join a Project" and copy/paste the Invitation Code. For additional security, each project will have a "Secret Word" which should be shared in a private way. With those 2 things, they will have access to the project!