The last one (FLA) is a built in player (possibly HTML5/Flash combined) for use in environments such as your workplace or school/college computer rooms where it may not be permitted to install extra software, but the use of webpages with multimedia is OK.
When promoting your station; it is good to share them all
and also the direct stream URL i.e
http://uk(n).internet-radio.com/:[port]/[mountpoints] (the last one only is found on icecast servers and the (s) is what server number you are on. this is the same URL you would give to live DJs.
Provided you use strong passwords for your DJs and admin; there is no danger hackers can get at your stream.and there are many applications and standalone equipment (such as portable "transistor radio" style Internet radios) where there is the facility to directly enter the stream URL; if you listen to a stream regularly this can often be quicker to do than navigating multiple webpages on a small screen device!
if this all seems confusing; think of your station not just as a "local" station but an international broadcaster; on the analogue HF (shortwave) frequencies they often have to give out several different frequencies for the same service as the reception conditions vary with time of day, weather etc.
It is therefore easier with internet broadcasting; as provided the correct URL is supplied, the stream is active and the network conditions good at both ends; the listener can always tune in...