When you create an invoice, it will be in draft status. A draft status indicates that invoice is likely to undergo further modifications and its amount is yet to reflect in your sales figures.
An open status for an invoice indicates that your customer is in receipt of the goods or services described on the invoice and the invoice is either fully or partially unpaid.
An invoice that has not been paid on time will be in overdue status.
A fully paid invoice will be in closed status.
If you have intentionally voided an invoice, its status would be shown as void. Click here for more on void invoices.
To visually identify the status of an invoice, Zoho Invoice provides a different color for each status. See the image below -
Zoho Invoice FAQ