very often I see, when I am looking in the vocabulary, those words have only one star. How decides the system which word is important?
My guess is that a word has more stars if it occurs in several items throughout the LingQ library, usually it’s the languages “top words” such as prepositions, adverbs and so on - words that don’t change forms too often (if at all).
**** examples from my German vocabulary: nachdem, obwohl, irgendwann, jedoch, inzwischen, sobald, sonst, statt, üblich, zwar…