Is It Better to Use a Nail or Screw to Hang Pictures & Things on the Wall?

Can anyone help explain what the white thing is and how to use it

Ways to Hang Things on a Wooden Door Without Nails : Nails, Screws

Drywall Screws: What to Know Before You Buy

7 Genius Picture Hanging Hacks to Make Hanging Art Easier

Level Hanging: Hang Artwork and Wall-hangings Straight and Level (DIY)

How to Hang Heavy Stuff

How to Put Screw Hooks in the Ceiling

How To Hang Pictures on Drywall (With or Without a Stud)

When hanging something with two hooks, use painters tape to get