A point to this:
Say you're a young woman, raised (as is still common for girls) to be quiet, maybe a little shy, definitely humble...it's not polite to brag, after all...and you encounter the Prideful Young Man. He starts talking about Slackware and how that's what real geeks use and listing off languages he knows (even if he only ever wrote a 5 line script in that language, he still lists it), and blah blah blah...bragging. You, being taught that one does not brag...believe that he does know all that...and much more, since of course he'll be humble and understate his skills. He, having been raised to...well...show off...interprets your "Oh, I just know Python" (with the unstated "fluently...but I also have used C and C++ and Java and Ruby on occasion...but I dont REALLY know them, so they don't count") as: ugh, noobie high-level programmer.
You end up with an inflated sense of what he knows. He ends up thinking you knows less than you do. And well...maybe you're just not 1337 enough for this group he's in. Maybe this isn't right for you. I mean, jeez, you're the same age and he's so much more advanced! You must not be good at this. That's it, this just isn't your thing. Hmm...maybe you'll go become a math teacher...
If you get past that point, you'll learn that in geek circles, overconfidence is the rule in stating your skills. You have to talk yourself up like it's a job application instead of being politely humble. It's intimidating until you realize this.
I spent the first year of university being intimidated of a group of guys in my class. Turns out we're pretty close in programming skills, and for Linux skills there's a range that I'm somewhere in the middle of.