Differences - Witchcraft vs Paganism
Both of these terms are umbrella terms, both are used in spiritual communities, but they are not the same thing. Many practitioners, especially new ones, and many outsiders use these terms interchangeably. They are not necessarily interchangeable.
Witchcraft is an umbrella term that can best be described as using magic to manipulate metaphysical or supernatural forces for a desired outcome. Witchcraft is an act; it's something that you do. There are many kinds of witchcraft, both the types of magic and how they work, and the types of specific witchcraft traditions. I have sections explaining both in this blog.
Paganism is best defined as any religion that is not one of the Abrahamic religions. This can be any religion outside of those, but is most commonly associated with religions that allow room for or encourage witchcraft. Many people forget that pagan religions can also include main religions in other areas that have nothing to do with witchcraft, such as Hindu, Shinto, and other such religions. Pagan religions are usually polytheistic, or having multiple deities, usually revere nature, and usually non dogmatic, encouraging thinking for yourself rather than following a staunch set of rules. Pagan religions also tend to not have a single holy text or doctrine.
You can practice witchcraft while being a pagan, or practice paganism while being a witch. Doing a spell doesn't make you a pagan. Worshipping ancient deities from non Abrahamic religions doesn't make you a witch. You can do witchcraft for your deities or your pagan religion, but you can't necessarily do paganism, rather you are a pagan or practice a pagan religion.
Some practitioners who claim the title of pagan, do so operating under the idea that pagan only means polytheistic non-Abrahamic religions, and that without the deities, you can't be pagan. This is inaccurate, you can very much be a non-theistic pagan, most who are work with the earth and sciences themselves, and for them, it's about the nature aspect. There are even some aspects of pagan that include S.A.S.S. pagans (Skeptical, Agnostic, Science-Seeking), and Atheopagan which completely disregards any deities or entities.
Wicca and Neopaganism is actually a major contributor to why the two terms are conflated so much. Neopaganism as a whole kind of took witchcraft and Wicca in as staples of the neopagan movement when Wicca became quite popular in the 70s and skyrocketed in the 90s and early 2000s. Because of this, a lot of media did what media does best; researched it a little bit, didn't quite hit the nail on the head, conflated the two, and popularized it quite substantially. Because the media was using the terms interchangeably, the people who were drawn to Witchcraft and paganism because of the media started using the terms interchangeably thinking it was accurate. And now with the internet and ease of access to widespread misinformation, it's boomed.
The widespread misuse of these two terms and using them interchangeably within the communities that they are a part of has led to such an immense amount of overlap that both communities have begun the discussion about whether or not language is simply changing with the times and it should be accepted and we move forward from there, or it should remain separate and true to their original definitions. As of right now, to my knowledge, the overwhelming majority on both sides seems to be preferring keeping it separate, but the conversation has begun and that in and of itself shows a changing of the times.