The formal visit or the call.
It is an art that is all but forgotten now but it was the lifeblood of Regency/Victorian society. It was a way of maintaining status and making sure niceties were observed. It also meant that women could choose to be *at home* or receiving callers on certain days. These were generally set days of the week. In London during the Victorian period, certain neighbourhoods divided up into given days of the week. So for example, Mayfair on a Monday. This made it easier to pay a number of calls in very quick succession. On other days, they could be engaged in other activities. Equally it meant that houses only had to be in the state to receive visitors on certain days. (I have some small sympathy with this approach as tidying up is not one of my favourite activities.)
Servants were informed. Women could be *at home* to intimate friends in the library but not to others. For a servant not to know if the occupant was in or out was considered very poor housekeeping.
The system was very formal and proscribed. These were not informal visits to friends but ways of maintaining the social fabric. The main injunction was when calling not to be a potted plant. In other words, you stayed for a short period of time, generally ranging between three and fifteen minutes. You might sip a cup of tea or coffee and you would engage in general conversation. It was considered bad manner to look at a clock. The proper lady was just supposed to know and leave. Women would often choose appropriate topics of conversation -- the weather or the latest play or places of interest to see. This way you would be less tempted to mention unmentionables.
There were strict rules about which room you were shown to. If you were seeing a male occupant, it would mostly be the study or the library. Or if you were visiting the lady of the house, it would be the drawing room.
Cards were also important. It was how friendships and basic social interactions were controlled. One left cards when one arrived in a city for example, within a few days of being invited to dine, after a dinner party/function, illness in the family, a death or if one was taking leave. Cards were used to form the basis of lists for invitations to balls for example. If a card/call was not returned within ten days, the caller knew the friendship would not be returned.
The calls after a marriage were some of the most important of a bride's life because it was when she could leave behind certain friendships without fear of censorship.
If one was leaving town and wished one's acquaintances to know of the matter, the initials p.p.c would be written on the left hand corner in ink. PPC stands for pour pendre change or to take leave. It simply meant the person was going, and was not considered a special note of admiration.
It appears to be a complex system but it was readily understood.