Suppose you want to return the total number of rows along with a column, you can write count(*) as shown below
select name,count(*) over () as total_rows from sysobjects
The result shows the value for name column along with total number of rows in total_rows column. Suppose you want to return total number of object types along with a column, you can write count(*) as shown below
select name,xtype,count(*) over () as total_rows,count(*) over (partition by xtype order by xtype) as total_types from sysobjects
The results shows values for column name , xtype and total number of xtypes for each xtype value. This count differs for each xtype.
This way you can make use of COUNT function without using GROUP BY Clause. From version 2012, you can also make use of SUM function for calculating running total using this technique which you can find at http://www.sqlservercurry.com/2012/08/sql-server-2012-running-total-with-sum.html