Vested benefits are the retirement assets that you have saved up to now in the second pillar. It is made up of the BVG contributions that you and your employer paid in during your working life, any purchases into the pension fund, and the interest income that the invested assets have earned over the years.
Whenever you change jobs, you take your vested benefits with you. Please note that you as the insured person are responsible for arranging the transfer from the previous to the new pension fund.