At some point in every witch’s journey the subject of familiars will arise. This particular piece of lore seems to create confusion and pop cultural influences haven’t helped understanding of what a familiar truly is.
Many of the old traditions contain written works (grimoires) that detail the process of conjuring a witch’s familiar. These are spirits called by a magical practitioner for specific purpose. Though they are often depicted in animal form, it is unfair to think of them as animals. Their unique kind of intelligence and nature makes them similar to Elemental beings or Fae. Familiars will work for their practitioners in exchange for attention, energy and offerings. Common types of work would be protection, locating lost items and even spying on people and places of interest.
Before you decide to include the conjuring of familiars in your practice remember they must be maintained. This typically involves an exchange of your energy and other resources.