A Maglet is used by witches to communicate by sending messages and pictures. Witches have had maglets for thousands of years. They are equivalent to non-magical tablets and phones.[1]
Mildred using Maglet to send a drawing to Maud
To send a message or Image, Just write the recipient's name on it and tap it three times. It even says who it's from. A Maglet can also be used to take photos, play games, and browse the witching equivalent of web sites (such as Felicity Foxglove's blog).
Ada Cackle's Maglet
Maud's Maglet in season 3
Back of Maud's Maglet in season 3