Rroma are organised in various subdivisions that, for a lack of a better term are called groups. The list of such groups is rather long, and each of them is further divided into smaller entities. To somewhat simplify the comprehension, let us present this social organisation in the opposite direction, namely from its core level upwards.
The first and most important level for Rroma is the family. The family, which can be rather large and span several generations is the centre of a Rrom's life. The first allegiance always goes to relatives.
The second level is the lineage, that is, the extended family: For example among Kalderaša, one finds Jonešti, Bumbulešti, Miheješti, Saporroni etc. These lineages take their names from some prominent old time leader or ancestor. For example, Jonešti is derived from Jono (John), Miheješti comes from Mihai (Michael). etc.
The third level of organisation is the "sub-ethnical" group. The groups, like Kalderaša, Lovara, Sinti, Čurara, Mačvaja, Zlotara and so on.
Groups are in a way "historical" entities which are bound together by a common history (where the group originally settled or wandered) as well as by common traditions and language - a dialect - and sometimes by common trades. The appurtenance to a group is more important than the fact of being Rrom.
Nomadic Rroma often exhibit additional structures inside of the group. Among these, one can count many Vlax Rroma who were travelling with horses and carts. This allowed them to maintain a high degree of their social organisation. The Kalderaša social organisation provides a good example of these structures, which are also valid for others.
In all countries in the world, Kalderaša are divided into nations: Serbian, Moldovan, Hungarian, Greek, Russian etc. A nation refers to the country in which they lived but rarely the passport they currently hold. There are for example quite a few Russian in France, Serbs in Russia, etc. These nations are an additional level above the lineages.
The Kalderaša who travelled and worked together formed a company, consisting of several families, not necessarily from the same lineage. The company's name is always derived from the name of its leader, the one representing the Rroma in front of the local authorities.
We have to add that the concepts of lineages and groups are evolving. Certain clans are "upgraded" to groups, as it happened with branches of Russian Lovara who now are "bona-fides" groups while some groups may be "down-graded" to lineages.
These levels were extremely rigid and have remained so in certain communities. Intermarriages, say, between a Kalderaš and a Čurara were almost unknown. Only recently has this become easier, in part because of the disintegration of these structures under repressive governmental measures.
The last level is the ethnic appurtenance, namely the concept of Rrom, and, by opposition, the Gadže or non-Rroma.