A Janya is a divine intelligence, often compared to either an angel or a deva, but best described as an emanation of Dea Herself, an aspect of Dea that has a particular focus and virtue ascribed to her. The plural of Janya is Janyati, and you will see various ways to describe them, such as the faces of Dea, the seven rays of Dea, the handmaidens of Dea, the seven celestial spheres, etc. The Janyati are of Dea, but also seen as distinct.
The Madrian term was originally 'Genia', and plural 'Geniae', from the Latin meaning of 'tutelary or moral spirit' who guides one through life(source). The Janyati are Dea's guiding light while we are inhabiting this material plane, and as such they have associated virtues and symbols alongside them to help us in our lives.
It may be helpful to review the classical model of the cosmos to understand what is meant by the Janyati spheres of influence and their realms, as it were. Classical astrology uses this model, and a good reading of that can be found here. You will see mention of the 'harmony of the celestial spheres' in conjunction with the Janyati often, and a good short read on that can be found here.
The Seven Great Janyati are our guiding Intelligences within Filianism, and are a most important aspect of the faith. They influence our daily lives, and you'll see this reflected in older styled calendars of the faith with each Janyati being a day of the week, and each year having a Janya for that year (depending on what day the Filianic calendar starts, this will note the Janya for that year). The next part of the lesson set will further delve into each Janya, her aspects, and her virtue.