: Specifies the hardware platform. This platform ID corresponds to the Aironet 1260 and 3500 Series .

: Reiterates that it's a tar archive.

The boot variable is pointing to an old file. Interrupt boot (Ctrl+Break at startup) and set correct BOOT variable:

Because these three platforms share the ap3g1 architecture, a single tarball ap3g1-k9w7-tar... can be used to upgrade or recover any of these devices.

To convert an access point from Lightweight to Autonomous mode using this image file, you must use a local TFTP server and a console connection. Need ios image for c3500 Access point - Cisco Community

, whereas "k9w8" refers to Lightweight/CAPWAP mode (controller-dependent).

This file turns a Cisco 3600/3700 series Access Point into a fully autonomous router/AP running IOS version 15.3(3)JF15.

: The file is a compressed archive containing the IOS binary, radio firmware, and the web-based GUI management files.

Denotes the software mode. The k9 stands for cryptographic capabilities (typically Triple DES and AES support). The w7 indicates that this is an Autonomous image (standalone). By contrast, an image with w8 indicates a lightweight (CAPWAP) image meant to be managed by a wireless LAN controller (WLC).

for setting up a basic SSID after you have flashed this firmware?