In modern times, retirement is pretty much exclusively through private investment accounts (401k and similar) into which your company may directly deposit funds. Nowadays it'd be a crazy risk to pin your retirement 100% on a single company. The company could fail, raid the pension fund, or just decide to not pay anymore. All those things happened and that's why we use private investment accounts now.
There are still some traditional pension plans, notably the US postal service. But they're very rare now.