A pond-less basin is a lined "pit" filled with gravel to act as a reservoir for a water feature. A submersible pump should be enclosed within the basin using some sort of vault, to protect it and leave it open for maintenance access. You can also incorporate void-filling basin matrix to store more water and use less gravel.
These units can be installed at the outlet of your plumbing and pump, as opposed to the inlet in the example above. Here the basin is a bog, and although it is a lined pit filled with gravel, it has a completely different function than to act as a reservoir. A bog is an area where water plants and beneficial bacteria can settle and multiply and is intended to clean very large volumes of water. You can also create a mini-bog, though, instead of using a waterfall filter box, if you would rather have a space to pack with water plants.