The Translation box expects an exact English word and will try to find the Spem words needed to express the equivalent, even if the translation isn't direct. The Meaning box searches an English phrase that describes the word's meaning and the query doesn't have to match exactly.
So for example if you want to find all the words that could be translated as 'of', search for that in the Translation box. If you search for that in the Meaning box, you might get for example a word that means "the opposite of".
On the other hand, if you remember the distinction Spem makes between the different meanings
of English 'of' but not what the words for them are, you could search in the Meaning
box for "association of" and you'd get
The Tags items allow filtering by categories, and Notes lets you enter a number of text strings which must be found in the notes field (search case-insensitively).
For convenience, either Enter while typing in a text field or Esc will submit the search.