The stere is a unit of volume and is a non-SI unit but accepted for use as a metric unit with the symbol st.
1 stere is equal to 1 cubic metre (1 m³) which is equivalent to the volume contained in a cube with edges all at 1 m. The stere is used to measure large quantities of cut wood or firewood. It is used to distinguish between cut and uncut wood - its equivalent, the cubic meter is used to measure uncut wood.
The word 'stere' hails from the Greek 'στερεός' or 'stereos' which translates to 'solid'. It represents the wood used to produce the cut wood - and therefore often the dimensions of the cut wood is less than its uncut equivalent.
The acre-foot is a unit of volume in the US customary unit system with the symbol ac⋅ft.
It represents the volume contained in a box measuring 660 feet long, 66 feet wide and 1 foot deep. This can be thought of a box the size of an acre but 1 foot deep.
It is approximately the same volume as an 8 lane swimming pool; 25 metres in length, 3 metres deep and 16 metres wide (assuming lanes are 2 metres wide).
It is still used in the US despite its links to the much-outdated imperial system of units. For example a "rule of thumb" is that an average suburban family's annual water usage should be around 1 acre-foot. This is equal to just under 3.4 m³ daily.