The first kind of keywords that you need to know about is short-tail keywords. They are normally made up of three words at the most. At times they are also referred to as head keywords. It is commonly known that short tail keywords are capable of fetching you a high amount of traffic but at the same time, they are highly competitive as well. Normally, people look for these keywords when they happen to be at the start of their research process. This is the reason why it is so hard to precisely point out the intent of people who are searching with these keywords.
The next name on this list is that of long tail keywords. They normally have 3 keywords at the very least but they are a lot more specific than the short tail keywords. The search volume for these keywords is also a lot less when compared to the long tail keywords. However, the main advantage of these keywords is that they are a lot less competitive. The most important virtue of these keywords is that you can always tell what people are looking for when they are looking with these keywords.
When you think of these keywords you have no option but to think of the recent trends in the market. A very good example of such a keyword would be Avengers Endgame. In fact, it can be any and everything that happens to be hot right now. The thing with such a keyword is that it remains at the peak only for a short period of time after which it tends to tail off. In fact, it has been seen that the drop is usually pretty sharp just as much as the rise. Keep this in mind when you use these keywords.
Evergreen keywords are ones that stay relevant at all times. It is true that the search volume would fluctuate every now and then but there would not be any wild change as such. From the point of view of the time, it can be said that the moment you publish something that focuses on such a keyword it would be relevant for at least 2 years. In this particular period, people would always like to look it up and read about it as well. Apart from these you also have product defining keywords, customer defining keywords, geo-targeting keywords, LSI (Latent Semantic Indexing) keywords, and intent targeting keywords.