What does 100 vested mean?

Answer 1

Vesting is an issue in conjunction with employer contributions to an employee stock option plan, or to a retirement plan such as a 401(k), annuity or pension plan.

A vested right is "an absoluted right; when a retirement plan is 100% vested, the employee has an absolute right to the entire amount of money in the account." It is a "basic right that has been granted, or has accrued, and cannot be taken away. Example: one's right to a vested pension."

There is two type of vesting, graded and cliff.

Graded means you get a certain percentage of your employer contribution each year, until you're fully vested. A five year grated plan would mean that you would have access to 20% of your employer contribution the first year, 40% the second, and so on.

Cliff means that you have no acces whatsoever, until your worked your vesting period. A five year cliff vesting period means you have no access to the employer contribution, until your worked that full 5 year period.

From: Wikipedia