This specific image is typically a Layer 3 (Router) image. If you need switching features (VLANs, Spanning Tree), you would look for a companion image with "L2" in the name.
Cisco IOL/IOU images are strictly intended for Cisco employees and authorized partners. For a fully legal alternative, consider Cisco Modeling Labs (CML) , which provides authorized Cisco images for a yearly subscription. i86bilinuxadventerprisek9ms1541tantigns3bin
It supports almost all the commands found on physical Cisco 15.x hardware. This specific image is typically a Layer 3 (Router) image
This signifies it is a Mainline release, typically used for stability. consider Cisco Modeling Labs (CML)