A vendor on your marketplace can access:
Dashboard Analytics
Orders
Products
Payouts
Messages (customer chat)
Vendor Store Connect (optional)
Settings
As is expected, a vendor can access data pertinent to only themselves. They have no access to the data and settings of other vendors.
You can also configure what they see to some extent. For example:
You can choose to hide customer information from their dashboard
You can share access to your integrated shippers with them
You can let them integrate their e-commerce store on their dashboard to keep products, inventory, and orders in sync.
You can review global settings for all vendors here.
To see the vendor view refer to: View a vendor dashboard.