What is the field (separated by :) in the file path listing?

Hi,

I see the following message from a link:
http://www.element14.com/community/community/designcenter/single-board-computers/next-gen_beaglebone//blog/2013/11/22/beaglebone-web-server--led-blinking

root@bbb-deb:~-- $ ls -l /sys/class/leds/beaglebone::/brightness
-rw-r–r-- 1 root root 4096 Nov 22 13:35 /sys/class/leds/beaglebone:green:usr0/brightness
-rw-r–r-- 1 root root 4096 Nov 22 13:35 /sys/class/leds/beaglebone:green:usr1/brightness
-rw-r–r-- 1 root root 4096 Nov 22 01:30 /sys/class/leds/beaglebone:green:usr2/brightness
-rw-r–r-- 1 root root 4096 Nov 22 13:35 /sys/class/leds/beaglebone:green:usr3/brightness

It is the first time I see ‘:’ in a path. Whether is it just like a general character in the path, or having special meaning?

I am new to Linux yet, though using for some time.

Thanks,