Ap3g3-k9w8-tar.153-3.jpo.tar [better]

The file is a specific Cisco IOS Software image used for lightweight Cisco Aironet Access Points . It is designed to allow these devices to operate in "Lightweight" mode under the control of a Wireless LAN Controller (WLC). Technical Breakdown of the Filename

Never try to untar this manually via Linux. You can , but you risk breaking the Cisco signature verification. Always let the AP’s bootloader handle it. Ap3g3-k9w8-tar.153-3.jpo.tar

If you are planning to upgrade your network to this version: The file is a specific Cisco IOS Software