Waste products

Ruins are what remains of a house or some other building when it has not been looked after for a long time and starts to fall apart.
Ruins of buildings that are very, very old are often considered to be very interesting, and people will come from a long way to look at them.

Scraps are small pieces of something, usually the remnants from cutting out what you want from something. Scraps can often be reused for other projects.
Scrap might also describe general waste that may or may not be able to be recycled, such as scrap metal.

Silt is very fine particles of dirt or soil that is carried along by water. Silt will eventually settle to the bottom of the water it is in, or like in the picture it gets washed up by water and then left behind when the water recedes.

A speck is a tiny piece of something, for example a speck of dust.

Stubble is the short stalks left when a crop like wheat has been harvested. Stubble is also used to describe other things that look like grain stubble, like the short hair on a man's chin that you can see a little while after he has shaved.

You waste something when you have it, but you don't use it, or you use it for less important things. Someone might waste their money by buying lots of pairs of shoes and then complaining later they have no money for other things.
Waste is also leftovers, or something that is no longer needed and becomes trash. Anything you throw away is waste.