Some years ago, Stable Value investments were mostly guaranteed investment contracts (GICs). GICs are contracts between an insurance company and a pension plan guaranteeing a fixed rate of return. Although GICs are fixed income investments like bonds, they are not subject to the up and down price change bonds experience with changes in interest rates. This is because the insurer guarantees the value will not drop because of interest rate changes.
In recent years, GICs became less attractive when compared to "synthetic GICs," also known as "wrapped bonds". These are high-quality, short to intermediate-term bonds (just like the bonds in a bond portfolio) that also have insurance aspect that guarantees the value will not drop because of interest rate changes.
It is generally considered that Stable Value investments have the price stability of a very short term fixed income investment like a money market investment, but with investment return that is similar to a longer term investment, like a three year to five year bond.
Investopedia – Guaranteed Investment Contract