Jump lists are like shortcuts to the files you use from within a program.You can access them by right clicking(arrow) on a program button on the taskbar or by clicking the arrow next to a program name on the start menu.Then click the item you want to go to.
To delete them just right click(arrow) the files and click delete from the dropdown menu.
Unless you right click these items you wouldnt even know they are there otherwise just right click the items and click delete if you want to remove items from them
To disable jumplists
Right click the taskbar
Select jumplists
untick the highlighted boxes and click ok