Trends

In my opinion, a fashion trend is is a style or item that is widely popular during a certain time. Nowadays, trends are often started by celebrities because they are encouraged to be experimentative with fashion and have a wide audience and a strong influence. However, trends are traditionally started by designers. Journalists watch these designer's shows and analyze them to try and find common themes, which some sites call "trend forecasting." This is because it takes time for fashions from a runway show to spread to the general public. Plus, by then, influensters such as bloggers and celebrities will have embraced or rejected the trend. 
Trends are kind of similar to memes. Internet users, often on Twitter or Reddit, will create tons of material that may or may not be funny. Popular users can facilitate the spread of a meme they find comical, and then once the general public catches on, it can go viral and even earn the status of "dank." 
Trends also follow the fashion cycle that I talked about in the post that I haven't finished yet. For example, 90's style tattoo chokers are a trend not because of a designer, but because of Gen Z's obsession with 90's fashion. However, not all 90's trends are currently in style, such as rice necklaces and slap bracelets, because the public chooses what they like and forgets what the don't. 
Now with the internet, trends gain speed faster, become bigger, and die harder. This is because the trend can reach a wider audience faster. But, the more prevalent a trend is, the faster people become sick of it, and the trend dies a brutal, cringe-worthy death. Just think of Angry Birds. They were fucking everywhere, and now you want to die a little on the inside every time you think of them. 
Back in the bad old days, trends were started by the wealthy and public, and people would copy them because they natually wanted to look like the wealthy. But without the rapid-fire communication of today, it would take years before most people found out what the cool cats were wearing, and so trends could last a lot longer.