I've very deliberately said sons in the title as I think it's very different conversations with sons and daughters.
My sons have always been aware I'm a feminist but as they grew up it was mostly me raising issues about the difficulties encountered in the work place. Now they are adults I realised they didn't have much awareness how much women do to remain safe. They had no idea I avoid late evening (networking) meetings because I'm scared to walk through the deserted station car park late at night. Or that even fat menopausal women get sexually harassed in the street (although not as much - joys of the menopause 
). They didn't realise that with every male colleagues I have to stay alert to be friendly but not to the extent that they misconstrue it and that threshold is different for every colleague (I think that's one reason I prefer working with much younger men, I don't have that stress). That I have to balance being knowledgeable but not 'show up the men'
Also that throughout their childhood as well as working everything they needed was thought about, tracked, sorted etc by me. (Their father still gets surprised that there's reduced shop opening times on a Sunday as it just doesn't impact his life.)
They knew the facts of life and how periods worked from school,but I realised they had no idea cycles could be very variable in timing and duration and that some women had particularly heavy and debilitating periods (especially some teenage girls as they settled into a regular cycle) and they'd never given any thought to the challenges of being an amateur athlete with periods. I ensured they knew mooncups don't suit every woman and that what a woman chose to use for sanitary protection was the woman's choice and not something they had a right to have an opinion on.
Watching the suffragette movie with them when it came out was a great way to get across how recent some of the rights women have now.
They are caring so bought into the idea of trans rights (and I believe everyone has the right not to be discriminated against so we're I n agreement there). One of them has a housemate that's relatively recently declared they are now a woman and my son reassured me they aren't at all pushy about the others getting their name/pronouns wrong and understand it's can be hard to make the mental switch. I pointed out that give them a bit more time and also that the first person they'd will get mad at about a mistake will be a woman And that when that happens I wanted my son to stick up for the woman because his voice as a male will be listened to much more than hers. Month later that happened exactly as I'd predicted and the ensuing drama and the realisation that he was able to stop the woman being harassed when he did step in (and that I'd predicted exactly how it would unfold) helped peak trans that son.
I've talked a lot about the erasure of lesbian rights and the cotton ceiling as this is an aspect I don't think they'd encounter or realise what was happening.
To really get through I've had to show some of the TRA posts on twitter, talk about what's happening on twitter and had to share some of the stories about men with AGP so that they really got why I didn't want to share female space with people like that. They did know a lot more than I'd have expected about MRA, incels and how abhorrent their views are (they educated me 
so that's been a useful comparison).
I've talked to them about mumsnet and explained it's ordinary women talking to and supporting each other, I talked to them about some of the non FWR threads so they could see the variety of discussions. One of my sons was particularly struck by the Ocado boycott and the power of a place like mumsnet.
These conversations have been very much over time, mixed in with other conversations and often in the car. It helps that we've always talked about politics, racism etc.
I'm not sure what I've missed that I should have covered so would appreciate any thoughts.
*They are of course free to ignore or reject any of what I say to them, they are adults I expect them to do their own investigation.