Vesting is an employee's right of ownership of retirement benefits. Employees don't have ownership rights to the contributions (and any earnings on those contributions) made by the employer on their behalf until they meet vesting requirements.

If you leave the co. in the first year, you don't get any pension or 401K match.

If you leave in the second year, you get 50% of what the company provides (pesion / 401K match).

Once you're "fully vested" (often times it requires 5 years), you get 100%.

What you put into the plan yourself is always yours.