These three words overlap, but they are not interchangeable. The differences matter when somebody is describing a religion, a practice or both.
Paganism
The broadest term. In modern use it usually covers nature-centred, polytheist, animist or reconstructionist paths that draw on pre-Christian traditions. Many Wiccans and witches identify as Pagan. Not all Pagans identify as witches or Wiccans.
See Understanding Paganism for the wider picture.
Wicca
A specific modern religious tradition that emerged in the mid-twentieth century, particularly associated with Gerald Gardner and those who followed. It typically involves initiatory structure (in its traditional forms), a dual deity of God and Goddess, and a ritual year. Some people practise solitary Wicca; others insist the word should be reserved for initiated lineage.
Not every witch is Wiccan. Not every Wiccan is comfortable being called a witch in every context.
Witchcraft
A practice more than a single religion. It can sit inside Wicca, outside it, or somewhere adjacent. Folk magic, ceremonial work, herbalism, divination and curse-lifting have all been called witchcraft by practitioners and by outsiders. Some witches are Pagan. Some are Christian. Some are atheist. The word has a long and complicated history of accusation as well as self-description.
Why the distinctions matter
If you are writing a dating profile, joining a group or trying to understand somebody else, precision helps. “I’m a bit witchy” and “I am an initiated Gardnerian” are different statements. Collapsing them into one aesthetic obscures more than it explains.
For relationships, the practical question is rarely the exact label. It is whether you can respect how the other person uses the words, and whether your expectations about practice, secrecy, and community line up.