What should I put in the target-audience field when setting up a listing?

I want to add info to the target-audience fields when adding a product and can’t find any documentation or suggestions on what to add into this field?

So for instance for a Christening gift should I add:
Kid
Mum
Dad

Or Should it be:

kids christening gift for celebration
mum mummy mothers christening day gift
dad daddy’s christening present

Where will this be displayed on the listing (if at all). Should I use commas to split up the list or have a single word on each. Any help appreciated as nothing could be found searching on this forum or on the web. Maybe no-one knows and it’s just a legacy field?

Thanks
Bob