I know Term store is the database for storing terms. But the question is where does it actually stores ? Is that in database or some other way? In a particular database? Can we access that?
Term store (database) is identified by you managed metadata service, and you choose the name of your service upon creation in Central Admin. I have my own descriptive name in my development environment:
You can also see the name in Central Administration > Manage service applications (in Application management section) > Highlight Managed Metadata Servie Type, and click properties. You should see the database name in the modal dialogue.
When you enable managed metadata in your SharePoint Server 2010 application, a managed metadata service and connection are created automatically. The service identifies the database to be used as the term store, and the connection provides access to the service. When you create new managed terms, or when users add enterprise keywords, these terms are stored in the database that is specified in the managed metadata service. When you publish a managed metadata service, a URL to the service is created. Before an administrator can create a connection to the service from another Web application, the administrator must know the URL of the service.
You can create multiple managed metadata services, and share multiple term stores and content types from multiple site collections. However, each managed metadata service must specify a different term store. When you specify a nonexistent database for the term store, a new database is created.
In order to use a Term Store in SharePoint 2010 you need to create a Managed Metadata Service Application for the farm. When you create this service application, a database will be created to host the term store. You will be prompted for a name for the database. That is the database that will store the term store. For details about creating a Manged Metadata Service Application see http://technet.microsoft.com/en-us/library/ee530392(v=office.14).aspx
You can then create term stores and term sets with the SharePoint browser interface from Central Administration or from any other site or web that you have sufficient privileges for.
You can import term sets from CSV files. A sample CSV file can be found as a link in the browser user interface when you create a new term set.
Term sets can also be managed with Powershell, and there are a number of third party tools for term store management.
As with all other SharePoint databases, the managed metadata database is created and stored in SQL, but you should NEVER try to manipulate it directly with SQL commands. This is not supported by Microsoft and may break SharePoint functionality.