Hello Patricia,
Those journals are all used for recording invoices; what journals your use and whether you use them at all depends on a number of things.
Vendor invoice:
I always try to use this form for recording invoices because it provides you with a single form for recording purchase order related and expense related invoices in a single form. Some people do not like it though because when recording expense related invoices, a category must be specified. Yet, the standard invoice import functionalities and workflows go with this form.
Invoice journal:
If you use for example the invoice journal then you cannot record purchase order related invoices and you need so somehow separate the purchase and expense related invoices before you receive them.
Invoice register:
This is the form/journal where you can alternatively record purchase order related invoices. Yet, when working with this journal, you always have a 2step recording process where the initial recording is done in the invoice register journal. Later on you have to use the invoice approval journal to transfer the registered invoices and then post the expense or link the invoice amount to a purchase order.
I would recommend that you test the different ways how you can enter invoices and make your own assessment before deciding for a specific way.
Best regards,
Ludwig
