Sawdust is the name for the fine particles of wood that are made when you cut wood up with a saw. In the picture you can see the pile of sawdust that has been made when the tree was cut.
Sawdust makes really good bedding for pet mice and guinea pigs.
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.
A speck is a tiny piece of something, for example a speck of dust.
Straw is a waste product from growing grains like wheat. It is the dried stalks of the plants after the seed heads have been cut off at harvest time. Straw is used for animal bedding, mulching gardens, as thatched rooves, making hats, and as a poor-quality animal feed. Hay is similar to straw but is a better quality animal feed.
Trash, rubbish or garbage is all the things that we don't use and throw away. You put your trash in a bin or trash can and it gets taken to the tip. Some people just litter the street with their rubbish.
Trash is mostly made up of plastic packaging from food, and scraps of food.