A Recovery Partition is a special partition on system hard drive intended to allow one to restore the system to factory settings in the event of system issues.
There are two types of recovery partitions.
One is created by installing Windows on GPT disk, which holds the WinRE. Typically Windows recovery partition only takes up several hundred MB disk space, as it only contains the bare operating system.
The other one, which appears to be the type you have, is created by the computer manufacture before delivery, which allows you to restore the OS to factory default settings, including OS, drivers and some build-in applications.
Look at the Lenovo manual for the steps to take if you wish to engage this option and restore ( reinstall) the system to the state it was in when Lenovo shipped it out the door.The operation will delete all data on the disk so, like RLGL advises above, a back up plan is always the first step in any such use.