Greetings,

Let me set this answer up -- I came into the Craft through a Coven, so I can give you he viewpoint from there. Also, because of being in several different communities over the years, I have practiced, most times in a coven, others less often , as a solitaire, I can give you the other side of the coin also. The term High Priestess is most always (there are exceptions) used as a term for the senior or in charge Priestess in a Coven/Circle/etc…,  this also hold true for the term High Priest. They are both terms and positions of recognition within the Coven, that the Coven as a whole has either recognized them as or has bestowed upon them. They are also in the outer community looked at as terms for these individuals that carry with them the Rights of that office and with those Rights, come also the responsibilities of that office. The are expected to have a vast store of knowledge and experience to draw upon, and be widely read and versed in any number of areas within the Craft and its religious aspects and Magicks. The terms Priest and Priestess are more general terms used for the Practitioners of Wicca. The terms to include ( but may not be limited to): 

1. The person has achieved a higher level of understanding as a solitaire and is more knowledgeable than their contemporaries (this seems a bit conceited) but also with this understanding is an awakening to the Gods that when it happens it is undeniable for they will seek you out if you try to deny them.

2. The person has achieved a 2nd Degree level of initiation within a traditional Coven - The 2nd Degree is the level of Initiation that recognizes one as a part of "The Wicce" and also bestows upon them the title of Priestess or Priest. This level also is also indicated by their ability to teach the Craft. It is also the precursor to clergy studies within the Craft.

Since the Craft(the Modern) was designed by Gardner after what he saw in many other magickal systems - with both an inner and outer court, The Outer Court being the Circle of the Postulants and 1st Degree Initiates. The Inner Court being the 2nd and 3rd Degree Initiates including also the Elders of the Coven. This is where most likely, in America, the separation of "The Wicce" and Wiccans came about. The Wiccans being the Postulants and Initiates but also the people in general that only attended ceremonies infrequently. This would also include those who believed in the old Gods but were unable to obtain the more extensive knowledge and training needed to lead the others in the Rites of the Old Religion. These people, I believe at least some of them, would later become what we now know as Hereditaries. I don't use the term Witch here, as most Hereditaries do not recognize themselves as Witchs. They are simply Hereditaries - The Wise Women and Cunning Men of the Heath. They are Priests and Priestess's in their own right, but may or may not ever call themselves such. The Terms Lord and Lady, are titles that n most cases are bestowed, whether by the Gods or by the Coven upon its leaders. And a title of a leader it is. For this title like that of High Priestess or High Priest also carry a weight of their own. It is the weight of power, and you will feel it the moment it becomes a part of who you are. Most persons in traditional Coven Craft are given the title to be added to their name at their final Initiation. So along with becoming a HPS or HP, they also become a Lady or Lord of that tradition or group. They may not be the senior HPS or HP, so they may not be able to use the title fully until they Hive off and have a Coven/Circle of their own, but it is theirs by right , they have earned it. So you can see that the Craft can accommodate both Solitaires and Coveners alike, with titles for those who choose them, for those who seek them, and for those who are called to them. 

Remember, One who is Properly Prepared, is never made a Fool to be.

Many Blessings

Lady Morgen

HPS Screaming Geese Coven