In SQL Server 2000 version, it is called MSAS (Microsoft Analysis Services).
From SQL Server 2005, it is called SSAS (SQL Server Analysis Services).
There are two modes − Native Mode (SQL Server Mode) and Share Point Mode.
There are two models − Tabular Model (For Team and Personal Analysis) and Multi Dimensions Model (For Corporate Analysis).
The BIDS (Business Intelligence Studio till 2008 R2) and SSDT (SQL Server Data Tools from 2012) are environments to work with SSAS.