'Count': Counts the number of non-null values.
'Count(*)': Counts the number of rows in the table, 
including null values and duplicates.

I agree with the above answer

Count(exp): Counts the number of rows excluding null values.
Count(*) : Counts the number of rows including null and 
duplicates records.

In SQL Server 2000,
Query:
------
select count from employees
Answer:
------
invalid column name 'count'


In SQL Server 2000,
Query:
------
select count(*) from employees

Answer:
-------
   No column name
   ----------------
1.  20

count - It returns the non null values
count(*) - It returns the null values and duplicate values

Count(expr) -> returns the number of records in the table 
where the expr is not null in the particular column.
Count(*) -> returns the number of all records in the table. 
(including duplicates and those with nulls)

Count(column name or exp) returns the no. of records for a 
specific/particular column of table excluding null values 
whereas Count(*) returns all the rows/records in the table 
including duplicated and null values

Count(column_name) returns the number of records in the 
table where the column value is not null for the particular 
column.
Count(*) returns the number of all records in the table. 
(including duplicates and those with nulls)