Invitation type(s) will be based off of what type of suppliers you are onboarding and what type of information is required based off of the supplier.
For example, you may have standard requirements for a new supplier to complete when being onboarded such as COI’s, W9’s etc.. but also have a slimmed down requirements for Independent Contractors. This would warrant two separate invitation types to handle the two different supplier requirements when registering.
Another example would be the type of product or service a supplier provides. This may be something the requestor is unaware of when inviting, so you may set up Categories to handle this so that the supplier selects during registration, and based off of their selection they are prompted with the different requirements based off of what they are providing.