A blue bar in search results generally signifies you found a file on the same LAN as you are using. I've never seen it personally.

Quality signifies your chances of successfully connecting to & downloading the file. Four stars is best. One star signifies you would struggle to connect to them (possibly a dial up user but could be someone with most of their upload bandwidth used up or minimal upload settings, else difficulty to connect to due to the isp hops between you & them (some ISP's in those hops may shape p2p bandwidth.))

# represents how many sources (people) have those files that the search was able to find.

? represents file type (icon represents your default player). 'Type' also represents file type (file extension). Size is file size. Speed is their connection type settings. Bitrate is the bit rate the audio file was encoded at.