What this will vaguely spoil: Near the beginning of the game, you find out that you're looking for two women, and you're asked by a powerful character to bring one in particular to meet him. This thread is meant to be a guide that allows players to reach the conclusion that they would prefer, while remaining as vague as possible with the exact details.
The Witcher 3 has more than one possible ending, although each ending changes depending on your other accomplishments and choices.