You would think that this question gets asked a lot, but the truth is people have so many ideas thrown at them from birth about witches that they don't often think to ask. We see witches as malicious cartoon characters or archetypes from stories that eat children and trick villagers. If not a cartoon, we see stereotypes of spacey, barefooted women in clouds of incense as they rave about astrology and your chakras.
While all of those things CAN be true, the expanse of what defines a witch is much larger than that. Witches are those who seek to understand and be in harmony with the natural world, who follow a belief system that emphasizes nature, the body, mind, and spirit- and connections to ancestors, deities and/or other worlds.
Witchcraft is not a religion. You do not need to hold any particular set of beliefs to qualify as a witch. There are witches that worship deities under hinduism, hellenism, christianity, and otherwise. There are also witches who solely acknowledge nature and don't work with any deities at all. Some work with ancestors. There are no rules.
The defining factor in your witch journey is your ability to see and appreciate the way things connect and create patterns. You can do that without ever holding a ritual or reading a tarot card. To see the way the seasons, the cycles of the moon, the cycles of our lives, and the way our thoughts and words impact our lives is a magic and a gift that not everyone knows or even seeks to know. That alone is witchcraft.
So you're a witch, now what?
If you do nothing else from here, that's enough. You count. However, you'll probably want some idea as to what paths you might want to journey down. Here are a list of topics worth researching and forming an opinion on as a newly realized witch:
Your ancestral heritage & their practices
Deities of different cultures and times
Moon phases and their significance
Spiritual cleansing & protection
Herbs and their properties
The list goes on forever, but there's more than enough to get you started. Happy witching!