Tane means capturing five animal cards (種札). It is worth 1 point, plus 1 point for each additional animal card beyond five.
Any 5 of these 9

February · Bush Warbler

April · Cuckoo

May · Eight-Plank Bridge

June · Butterfly

July · Boar

August · Wild Geese

September · Sake Cup

October · Deer

November · Swallow
Tane is a counting yaku: the more animals, the more points. It combines with Ino-Shika-Chō (the Boar, Deer and Butterflies are animals too), so a strong animal pile often scores both — 5 for Ino-Shika-Chō plus the Animals count.
Animals are common, so Tane builds naturally through a round. It's a good reason to call Koi-Koi when you already have five animals, several more are still unaccounted for, and your opponent isn't close to scoring: each extra animal is another point, with no new set to complete.
There are nine animal cards in the standard deck used here. Five animals score 1 point; each animal after that is +1. The Sake Cup is one of those nine — never leave it thinking it is only useful for viewing yaku. A pile that already has Ino-Shika-Chō will often cross five animals without much extra work.
Animals (Tane) uses the same Nintendo-style Koi-Koi scoring on Hanafuda Legends whether you play ranked, casual, private rooms, or vs computer. Set yaku replace smaller versions of the same family (you do not score Sankō and Shikō together), while unrelated yaku such as ribbons, animals and chaff still add to your total when you stop.
If you are new to the combination, practise in the tutorial or against the computer first, then take it into online play. How to Play covers the turn structure, matching, and when to call Koi-Koi versus stopping for points.