What exactly difference between Upgrade.bat and Update.bat .Which file needs to be used for upgrade from 8.8.1 to 24.1.2

When we look at webpage in PegaPlatform media D:\Pega\118061_Pega_24.1.2\StartHere.html then it says as mentioned below.

The Installation and Upgrade Assistant tool requires a Java runtime environment. The command line scripts equivalents are in the /scripts directory of the Pega Platform media named: install.bat, install.sh, upgrade.bat, and upgrade.sh. 

Few articles says run Update.bat.

1. If you have not done so already, edit the setupDatabase.properties file.
   1. Open the setupDatabase.properties file in the scripts directory of your distribution image: Directories/distributionDirectory/scripts/setupDatabase.properties.
   2. Specify the appropriate options for your update. For each option, add the appropriate value after the equal sign.
   3. Configure the connection properties. Use the existing schema names for the rules schema and data schema names.
   4. Optional: If you have a separate customer data schema, set the target schema name:

      pega.target.customerdata.schema=existing-customer-data-schema

   5. Optional: If you are repeating a failed update, configure the resume property:
      • To resume the update from the last successful step, set automatic.resume=true.
      • To restart the update from the beginning, set automatic.resume=false.
   6. Save and close the file.
2. Open a command prompt and navigate to the scripts directory.
3. Run either update.bat or update.sh