I don't know what to tell you. If you don't know what "CTF" is you're not the target of this blog post. It's like stumbling upon article "What's new in HTTP/2" and complaining that "HTTP" acronym is not explained.

I don't mean that everyone must know what CTF is, but sometimes it's OK to write things just for your community (CTF community in this case), not for general population.

Capture the flag the only expansion of CTF that i know but even if it is capture the flag this still doesnt make any sense. Like Quake CTF?