Care to explain what Twitter, Tumblr, Instagram and Facebook are?

[Sky]

Obviously this question sounds a bit odd coming from a 17-year-old girl seeing as most would assume I use all of these social media sights. But, I'm not really sure what the point is. Take Twitter for example. I just don't see what's so cool about snapping selfies, pictures of what I'm having for dinner and quoting other people. Maybe it's just me. It's just hard though because evryone at school is telling me to get make Twitter and Instagram accounts, and when I say I don't even know how Facebook works they look at me like I'm from another planet. Oh, and I'm just gonna add that I'm not from America, I only came here a few years ago, but I'm not sure that makes much difference because other countries have social media too.

So, if anyone cares to just explain exactly what these sights to me. also, please don't call me stupid even though I do feel kinda stupid being behind on the trends. Thanks