[DAVES]

My aunt who was an artist and would regularly change the artwork on display had what it think was called picture hanging molding.

The artwork is secured by hooks that attach to the molding.
Strings are hung from those hooks. Result you do not put holes into the wall and you can easily change the art and or it's position on the wall.

As to how to hang pictures there are hundreds of answers
It depends on weight of what you are hanging and what you are hanging it on.

Some items now are sold with keyhole slots cut into the back.
This system is sued because it is cheap. Also, the company usually supplies no instructions and the system allows no adjustment for level or height. The secret is to make a full size paper model of the item secure that to the wall with the blue removable masiking tape and then drill through the pattern.