Prokaryotic cells are simple, single-celled organisms. Their middle is an open space, not divided by membrane walls. It lacks a nucleus and it has no membrane-bound organelles.
Instead, the DNA of a prokaryotic cell is found in the nucleoid. The DNA typically consists of a circular chromosome, making one large loop of genetic material. Cytoplasm fills the inside of the cell, suspending the components inside the prokaryotic cell. Ribosomes are found in the cytoplasm, which the cell requires in order to synthesize proteins. A plasma membrane wraps around the inner components of the cell, separating those from the cell's environment.
A cell wall helps the prokaryotic cell hold its shape and provides some protection. Most cell walls are covered in carbohydrates, which are sticky and help the cell cling to various surfaces in its environment. Some prokaryotic cells have a flagellum, which is a long, tail-like structure that helps the cell move. Some also have fimbriae, which look like hairs that help the cell attach to other surfaces. And some cells have pili, which the cell might utilize to transfer DNA to other bacteria and might employ as a means of movement.
Their simplicity means that prokaryotic cells don't necessitate much space, and most are therefore significantly smaller than eukaryotic cells.