You would use the Processes tab to show each individual application's demand on the system's resources, while Performance tab is used to see the overall total usage on your systems resources.
Task Manager, previously known as Windows Task Manager, is a task manager, system monitor, and startup manager included with Microsoft Windows systems. It provides information about computer performance and running software, including name of running processes, CPU and GPU load, commit charge, I/O details, logged-in users, and Windows services. Task Manager can also be used to set process priorities, processor affinity, start and stop services, and forcibly terminate processes.
The program can be started in recent versions of Windows by pressing ⊞ Win+R and then typing in taskmgr.exe, by pressing Ctrl+Alt+Delete and clicking Start Task Manager, by pressing Ctrl+⇧ Shift+Esc, by right-clicking on the Windows taskbar and selecting "Task Manager", or by typing taskmgr in the File Explorer address bar.
Task Manager was introduced in its current form with Windows NT 4.0. Prior versions of Windows NT, as well as Windows 3.x, include the Task List application, are capable of listing currently running processes and killing them, or creating new processes. Windows 9x has a program known as Close Program which lists the programs currently running and offers options to close programs as well shut down the computer.