client layer: The layer that resides closest to your application, and that your application uses to communicate directly with Windows Azure SQL Database. The client layer can reside on-premises in your data center, or it can be hosted in Windows Azure.

infrastructure layer: The layer that represents the IT administration of the physical hardware and operating systems that support the services layer.

master database: In SQL Database, a database for performing server-level administration by using a single database. The master database keeps track of which logins have permission to create, alter, or drop databases or other logins. You must be connected to the master database whenever you CREATE, ALTER, or DROP logins or databases. The master database also provides access to the firewall rules and SQL Database usage metrics that you can view.

platform layer: The layer that includes the physical servers and services that support the services layer. The platform layer consists of many instances of SQL Server, each of which is managed by the SQL Database fabric.  

service administrator: The person responsible for setting up and managing your SQL Database service.

server-level principal: An account that is similar to the sa login in SQL Server. During the provisioning process, SQL Database creates a login for you that is the server-level principal of your SQL Database server.  The SQL Database server-level principal account has permission to manage all server-level and database-level security.

services layer: The layer that functions as a gateway between the client layer and the platform layer, where the data resides. The services layer provides three functions: provisioning, billing and metering, and connection routing.

sharding: A technique for partitioning large data sets, which improves performance and scalability. Sharding also enables distributed querying of data across multiple tenants.

SQL Database fabric: A distributed computing system composed of tightly integrated networks, servers, and storage. The SQL Database fabric enables automatic failover, load balancing, and automatic replication between physical servers.  

SQL Database Federations: SQL Database Federations provide the ability to scale-out database tier of applications. Federations represent a dataset that is spread over many nodes and manage connection routing and online repartitioning to help scale database tier on demand. 

SQL Database Migration Wizard: A wizard that helps you select your SQL objects, create SQL scripts suitable for SQL Database, migrate data between on-premises SQL Server 2008 or SQL Server 2005 and SQL Database servers, as well as between two or more SQL Databases in the same or different data centers. The SQL Database Migration Wizard is community-built, and is not supported.

SQL Database portal: A user interface that you can use to provision servers and logins, and to quickly create databases. SQL Database portal is replaced by Windows Azure Platform Management portal.

SQL Database provisioning process: A way of preparing and configuring the hardware and software required to maintain your data at a Microsoft data center. The SQL Database provisioning model describes the logical hierarchy of your Windows Azure platform account, SQL Database servers, and databases; by using this process, you can rapidly provision your data storage. 

SQL Database server: A logical group of databases that acts as an authorization boundary and central administrative point for multiple databases. Each SQL Database server includes logins similar to those in instances of SQL Server on your premises.  

sys.bandwidth_usage A view that describes the bandwidth used with each database.

sys.database_usage: A view that lists the number, type, and duration of databases on the server.

tenant: TBD

TDS Gateway: The TDS Protocol Gateway unit functions as a gateway between your application and the underlying platform, where your data resides. It performs the functions of data center isolation, provisioning, billing and metering, and connection routing.

Windows Azure SQL Database (brand): A cloud-based relational database platform built on SQL Server technologies. By using SQL Database, you can easily provision and deploy relational database solutions to the cloud. You can also take advantage of a distributed data center that provides enterprise-class availability, scalability, and security with the benefits of built-in data protection and self-healing.