When people ask what femmes are, or, worse, what they're for, I am always tempted to counter-ask, "So what are mechs for?" I really don't like having females being treated always as the anomaly, as the only gender that has gender. tiamatschild has a good rant on that here (http://tiamatschild.livejournal.com/380805.html), from before I was in the fandom.
That said, in most Transformers fiction, if not necessarily most Transformers canons in-universe (it's relatively easy to assume that both TFA and Beast Wars have a fairly even gender distribution), female Transformers are a small minority; it's more a problem with the canon than with the fans asking the question. So I'll put the real-world gender issues aside from the moment and try to answer the question on an in-universe personal-canon level.
The answer, there, is that I don't really have one; I'm really, really opposed to there being a canonical answer to this, because so far Transformers canon has given us "a female Transformer was created to appease earth feminists" and "a female Transformer was created by a mad scientist and his victim is a homicidal maniac because of it". (Or so I gather; I haven't actually read Spotlight: Arcee, because I suspect it will make me really angry.) Given that, I'm really pretty okay with no explanation.
(And, whoops, so much for leaving IRL gender issues out of it. Anyway.)
In terms of fanon--I write the females as having the same parts as the males, sexual speaking. In G1, often I treat it broadly as a frame type/specialty; judging from the canon evidence, G1 femmes are mostly guerilla warriors. Except on Paradron, where they appear to be medics, but, then, everyone on Paradron is a pacifist, so clearly there had to be some shifting of specialties. And on Junkion, where they're television addicts like everyone else.
The other way I look at it is that it's a matter of gender identity, part of a TF's base programming or spark; the term 'femme' actually tempts me to refer to the males (or some of the males, anyway) as 'butches', and consider TFs to be essentially a bunch of lesbians. Which would be fun, but isn't anything I've ever actually written.
The other thing I've not-actually-written, gender-meta-wise, is the converse to Spotlight: Arcee, in which a mech is turned male by a mad scientist and freaks the hell out of it, because he was gender neutral before and suddenly everyone is calling him he and it's all very traumatic. Meanwhile all the humans are terribly confused, because they already thought he was a guy...I should actually write that at some point, but I keep getting distracted by Galvatron/Cyclonus porn.
TF gender
That said, in most Transformers fiction, if not necessarily most Transformers canons in-universe (it's relatively easy to assume that both TFA and Beast Wars have a fairly even gender distribution), female Transformers are a small minority; it's more a problem with the canon than with the fans asking the question. So I'll put the real-world gender issues aside from the moment and try to answer the question on an in-universe personal-canon level.
The answer, there, is that I don't really have one; I'm really, really opposed to there being a canonical answer to this, because so far Transformers canon has given us "a female Transformer was created to appease earth feminists" and "a female Transformer was created by a mad scientist and his victim is a homicidal maniac because of it". (Or so I gather; I haven't actually read Spotlight: Arcee, because I suspect it will make me really angry.) Given that, I'm really pretty okay with no explanation.
(And, whoops, so much for leaving IRL gender issues out of it. Anyway.)
In terms of fanon--I write the females as having the same parts as the males, sexual speaking. In G1, often I treat it broadly as a frame type/specialty; judging from the canon evidence, G1 femmes are mostly guerilla warriors. Except on Paradron, where they appear to be medics, but, then, everyone on Paradron is a pacifist, so clearly there had to be some shifting of specialties. And on Junkion, where they're television addicts like everyone else.
The other way I look at it is that it's a matter of gender identity, part of a TF's base programming or spark; the term 'femme' actually tempts me to refer to the males (or some of the males, anyway) as 'butches', and consider TFs to be essentially a bunch of lesbians. Which would be fun, but isn't anything I've ever actually written.
The other thing I've not-actually-written, gender-meta-wise, is the converse to Spotlight: Arcee, in which a mech is turned male by a mad scientist and freaks the hell out of it, because he was gender neutral before and suddenly everyone is calling him he and it's all very traumatic. Meanwhile all the humans are terribly confused, because they already thought he was a guy...I should actually write that at some point, but I keep getting distracted by Galvatron/Cyclonus porn.