The webpage on the left is a display copy¹ in which all words² have been linked via Multidict to a selection of dictionaries for the benefit of language learners.
If a word appears with a black background when you hover over it, then you can click on it to look it up in a dictionary.
Multidict will allow you to swap easily to different dictionaries and different target languages if you wish.
1. So any forms, for example, will not work.
2. Except possibly for words which are part of an existing link.