The trend is a famous word for the things that are famous in the context of the current affairs that are going on worldwide or in a specific geographical area. Based on this, Google introduced an effective search engine result feature that singles out all the trends and presents them to the users to ensure they are as updated with the world as they are.
The trends are almost always related to specific geographical areas because of the difference of the lifestyle and governing factors that are different in each region. There are very small chances of a trend going worldwide unless it is concerned with a topic that affects people all around the globe.
For Example, Greta Thunberg was trending on the world news when she tried to make the world focus on the issue of Climate Change and Global warming because they are the real problems that humanity as a single entity is facing.
As for Google, the search for the hot topics that are doing the rounds of the internet and getting people together to discuss ends on their own search engine. Their method of finding the material for the Google Trends is quite simple, the only thing they need to do is analyze the most searched topics, worldwide as well as geographically, in a specific period of time.
Not only for themselves but for the users as well, Google has provided us with the tools to find out the popularity of the topics that have been featured as their trends.
Along with them are also the graphs to show you how much the topics were in trend and for how long, how many days it remains a trend, and how many days since it goes into oblivion (basically the prediction of the time it will no longer be in the Search Engines Results Pages, SERPs, anymore).
From the point of view of a website owner who is trying to perform better on the SERPs and get more organic traffic on their website, this tool is fairly useful because it helps them find the most trending keywords related to their topics and at the same time predicting the success rate as well the duration of the usefulness of them.
One more feature to help you in finding the perfect keyword for your optimization effort is of comparing them. If you have any doubt about which keyword will be more of help to your content you can just compare them on this tool.