Hi Sabeera
If the Reports and Dashboards tabs are exposed in the community, external users can access reports and dashboards with some limitations.

Important:-
To allow external users to create and edit reports, your organization must use the enhanced sharing model. See Analytics Folder Sharing.

You can give permission to create and edit reports to communities users with the following licenses:-
Community licenses
Customer Community Plus
Customer Community Plus Login
Partner Community
Partner Community Login

Portal licenses
Customer Portal Manager
Customer Portal Manager Custom (for Enterprise Administration users)
Customer Portal Manager Standard
Customer Portal Manager User
Gold Partner
Ideas Only Portal
Overage Customer Portal Manager Custom
Overage Customer Portal Manager Standard
Partner
Silver Partner (”Export Reports” permission isn’t available to this license)

Note
These permissions aren’t available to high-volume user licenses, such as Customer Community, High Volume Customer Portal, Service Cloud Portal, and Authenticated Website.
External users with legacy portal licenses can create and edit reports in communities, but not in portals.

After you grant permission to your external users, they still can’t:
 1) Schedule reports or dashboards for email and refresh at a specific date and time
 2) Create, edit, or view reports in the Unfiled Public Reports folder

All role-based external users in your community can refresh dashboards set up with “Run as specified user” and “Run as logged-in user” up to 1,000 times daily per org. Scheduled and automatic refreshes don’t count against the limit. There is no refresh limit for internal users.
All role-based external users can be selected for the “Run as specified user” option.

 You can go on the following link for the further query.
(https://help.salesforce.com/HTViewHelpDoc?id=limits_communities_analytics.htm).

Please mark it best answer if it helps.
thanks