A slicer is a sort of third axis in a query that filters data. The other axes are the row axis and the column axis. A slicer defines a logical slice of the server cube by instructing the server to ignore all values not part of your slice. For example if you were running a query for general category stores, you could apply a slicer that slices the category stores into store subsets, such as computer stores, discount stores, and electronic stores.
When working with a slicer, use only an individual member from a dimension. The dimension cannot be used in a Top Label or Side Label (no dimension can be represented on more than one axis at any time).
To specify a slicer:
Click Slicer on the Section title bar to open the Slicer pane.
Select a member from a dimension in the Catalog pane and drag it to the Slicer pane.
Every dimension folder contains a members subfolder named “Values for …” that domain. The subfolder contains the members eligible for selection in the Slicer pane.
If you are running in Hardwire mode (see Processing OLAP Queries Automatically), the slice is applied instantly.