Structure — Multilevel Multi-Selectable lists
It's a place to keep the lists of difrient value's types.
You have a "Structure" tab in extra search, create a parent there like "animals" and create it's children — "cat", "dog" etc.
Then in your table create a new field with ExtraSearch type and in "Parameters" box put the structure parent name "animals" and a selection method (single or multi) "animals,single"
Then in a module use this field instead of the one you have now with "string" type.