Each line under a word is one phrase the word belongs to, in the phrase's colour. A word with several lines is in several phrases at once, usually a short phrase inside a longer one. Up to 3 lines are drawn; +N means the word is in N more. Hover a phrase, a chip above, or a word, to see which is which. The ayah stays pinned at the top while you scroll through its phrases.
These phrases look like duplicates
Same ayahs and the same words. Merging moves every ayah into the phrase you keep (the stronger review decision wins when both have an ayah) and deletes the others.
Phrases of 3 or more words (or the whole ayah when it has only 2) that also appear in other ayahs, word for word or with small differences. These are suggestions, nothing is saved until you review and approve a phrase.