YITH WooCommerce Email Templates allows you to customize the style of the standard WooCommerce emails. You can use a different template for each email and choose from the 4 default ones included in the plugin.
By integrating Email Templates with Multi Vendor, you (admin) will be able to customize the layout of all the additional emails made available by YITH WooCommerce Multi Vendor. They will automatically appear in the list of all editable emails in YITH > Email Templates > Settings.
For more details about YITH Email Templates, please, refer to the official documentation here.