Authentication for Document Access in SharePoint

Question

We have an Intranet SharePoint site. When logging into sharepoint, we dont give domain name. We simply use the format username and password.

But when accessing a document, we are not able to access without giving domain name.

When accessing a document we use the format domain\username and password.

 

My Questions are

Why the domain name is prompted during document access???

Is there a way to access documents in sharepoint without giving domain name??

 

Thanks