do you know what it is? is it moisture or is it old paint falling down?

[gato]

 

[AndersS]

Looks like a basement wall that is or has been damp, with paint/plaster that has partially peeled off. Some salt deposit as well due to moisture. If nothing is addressed, the moisture issues remain.

 

[Davidofsweden]

Hello.
It also looks like moisture on a basement wall.
If you want to see if there is still moisture in the wall, tape a plastic bag to the wall. If moisture appears on the bag, then there is moisture in the wall.

 

[Anna_H]

Old paint does not fall off unless there is or has been moisture.

 

[topmount]

Could be painted with the wrong type of paint as well, then even non-critical levels of moisture can make it look like that.