On a typical rollover, your 401(k) holdings are liquidated and a check is sent to you or the destination institution for the balance of your investments at the time of liquidating. There are some scenarios where your holdings can transfer to your new institution in-kind, but this is less common.
Your investment options in the new plan might differ from those in your old 401(k). You will likely need to select new investments that align with your retirement goals. Some plans offer tools to make this process easier or even fully automated.