In a simple case statement, one value or variable is checked against multiple possible answers. The code below is an example of a simple case statement:

SELECT CASE DATEPART(WEEKDAY, GETDATE())
    WHEN 1 THEN 'Sunday'
    WHEN 2 THEN 'Monday' 
    WHEN 3 THEN 'Tuesday' 
    WHEN 4 THEN 'Wednesday' 
    WHEN 5 THEN 'Thursday' 
    WHEN 6 THEN 'Friday' 
    WHEN 7 THEN 'Saturday' 
END

In a Searched Case statement, each option can test one or more values independently. The code below is an example of a searched case statement:

DECLARE @FirstName varchar(30) = 'John'
DECLARE @LastName varchar(30) = 'Smith'

SELECT CASE
    WHEN LEFT(@FirstName, 1) IN ('a','e','i','o','u')
        THEN 'First name starts with a vowel'
    WHEN LEFT(@LastName, 1) IN ('a','e','i','o','u')
        THEN 'Last name starts with a vowel'
    ELSE
        'Neither name starts with a vowel'
END