The V sign in the UK is usually an insulting gesture, it is made with the back of the hand pointing towards the person being insulted. There are various stories about when it started the main one being that it was english archers insulting the French in medieval times. https://en.wikipedia.org/wiki/V_sign Churchill however famously used it as a symbol for victory during WW2, the important difference is that the palm of the hand is pointing outwards.

Having colleagues and friends in the UK, I can agree with Simon when he says that its an insulting gesture in the UK. I also agree about its associations with WWII. However, in the US, the "V sign" is simply a peace sign. Many people associate it with the hippie movement in the 1960s in the US. Back then, it was a symbol for anti-war (peace). It also has some associations with US hip-hop culture. Today in the US, it still means "peace," although most people aren't thinking about wars when they use it. You'll mainly see someone use the gesture in selfies or group photos and its still seen in hip-hop culture. Having studied in Taiwan, I can say that the sign is used a lot more frequently in Taiwan than in America (not sure how that compares to China). In selfies/group photos in America, I would say most people use it lightheartedly--you'd probably see someone using it in a "funny photo" where people are making silly faces, have their tongues out, and other funny things. If I were to take a photo with a friend, I wouldn't use the peace sign unless we were taking a funny photo, and even then, I wouldn't use it all the time. All this to say that there is a major difference in how this sign is used today in the UK and US, even though we are both English-speaking countries.

I've always wondered why so many Asians have V-shaped hands in their photos and wondered what it meant. I know that it was a military symbol in the 1940s during World War II (V for Victory), but I have never seen an American or Canadian use it during the 1980s or 1990s or 2000s.

I don't live in an English speaking country, though I've ever read before about that means the "victory hand", used by the allies at the world war 2. I also hear that, when you do it showing the back of your hand, it's a very offensive gesture at the British culture. I am not sure about that things, though.

Mostly we associate it with hippies and the 1960s, or with Asians taking photos. I'd say it doesn't really carry much significance for us nowadays. The important thing is to do it with the palm/inside of the hand forwards. If you have the back of the hand facing forwards with the first two fingers sticking up, in the UK that's a very old (but still used) gesture meaning something along the lines of "f*** you!".