The Script task provides code to perform functions that are not available in the built-in tasks and transformations that SQL Server Integration Services provides. The Script task can also combine functions in one script instead of using multiple tasks and transformations. You use the Script task for work that must be done once in a package (or once per enumerated object), instead than once per data row.
Do not use this tag for the SSIS Script Component, instead use script-component.
Check the following article for more information: SSIS Script task vs. Script Component
Based on the official SSIS documentation, SSIS tasks are categorized as the following: Data Flow Task, data preparation tasks, workflow tasks, SQL Server tasks, Analysis Services tasks, maintenance tasks, custom tasks, and scripting tasks.
The SSIS Script Task extends the package functionality by using scripts. It performs functions that are not provided by the standard Integration services tasks.
