By purchasing the annuity's GLWB, you can help secure an income stream for the rest of your life (and your spouse's*, if you choose) that's protected from market losses and has the potential to increase with market gains.2
*A spouse is considered a married partner. In some states that can also include a domestic partner or civil union partner.
Let's say you purchase a variable annuity with a GLWB. A few years later, the market falls, reducing your annuity contract value. The GLWB provides a protected payment base of income which won't fall due to the market. Note: the GLWB protects your income only, not your contract value.