An estate is a group of islands that are under common management.
For instance, you can appoint one or more estate managers. That person can, for instance, ban someone from the entire estate (from all islands in the estate).
You can pick a different name for the island and for the estate, but there's nothing stopping you from reusing the same name if you want.
From: Henry Grumiaux
Estate: Parana
Island: Curitiba
Does it makes my island with the name of Parana Curitiba ? (or Curitiba Parana) ?
This is a good example. Curitiba is a city in the Brazilian state of Parana. All cities in Parana are presumably governed by the same state laws. City/State in RL is sort of how Island/Estate works in SL.
However, the name of the island is simply "Curitiba". The estate name Parana is only visible in a few places (for instance, if you visit Curitiba island and then click on World --> Region/Estate --> Estate tab).
You can reuse the same name for both island and estate (for instance, in RL, "Sao Paulo" is both the name of a city and a state in Brazil).
From: Henry Grumiaux
Ah, when I choose a place on the grid.I need to make reservations surrounding my islands if I've plans to grow and create a estate (if estate is really a group of islands)
All eight positions bordering an island (or an existing reservation) are automatically protected (north, south, east, west, northeast, northwest, southeast, southwest), so no one can put an island there without your permission. But if you want to be sure that you can expand, you should buy reservations in surrounding grid locations.