Script : This WORD is used in automated Testing(Like 
QTP,WR,Etc). Here We Record and Run the appln or jus type 
in the actions to be done in the appln in the automation 
tool. The Lnaguage thats displayed wen u record n run or 
type in the actions that r to be done is called a SCRIPT.
Usually in WR it is the C Language Format
while in QTP its the VB Script Format

Test Cases : This word is mainly used in Manual testing.Any 
Appln needs a TEST CASE.A TC will conatain the action of an 
appln.Here we dont have any tool.Everything here is 
manual.a Tc contains the following :
Name of the TC
Req no
Mod name
Severity
Test Data
Pre condition
Brief Desc
------------------------------------------------------------
sl no
Desc
Input
Expected Result
Actual Result
Status 
Comments
------------------------------------------------------------
Author
Reviewed by
Modified by
Last Modified date

Script is to navigate the application ...

Test case is validate the functionality....