Like drops of rain falling on the roof, vocabulary of all different kinds enters our minds and then will often fall away to the sides. We want to catch those rain drops (vocabulary) and keep them.
So we take notes on whatever we can, a piece of paper, a textbook, in our phones. Some words in our textbooks are very important to us, and others aren't. Just as all rain finds the lowest point it can fall to, whatever important vocabulary enters our lives needs to find its way to one place our vocabulary book. This is our go to place for revision, that we come back to, that we can use as a starting point in language exchanges, that we can add details about each item, practice writing it, adding a secondary definition, example sentences.
It doesn't matter where we keep the rain, it could be on a website, or in a notebook. But there should be one place.
Some vocabulary with appear so often that we will know it without trying. But each drop of rain has its own beauty, especially as the flow in speech.