What does "membrane-bound" organelle or "nonmembrane-bound" organelle mean?
Eukaryotic cells contain membrane-bound organelles, meaning that these organelles (e.g. mitochondria, lysosome, etc.) are surrounded by a phospholipid bilayer (membrane). This allows organelles within the cells to control what enters and leaves it by using a selectively permeable membrane.
A nonmembrane-bound organelle simply means that the organelle doesn't have a membrane (e.g. centrioles, ribosomes, etc.) because they don't need to control their internal conditions.