There is a usual arrangement of where the orchestra is seated when they are performing and also practicing. The usual is that the violins are positioned to the left side of the conductor always and usually at the back are the percussion group. This two is the standard and others could be arranged according to the preference of the conductor. Space that is given also is considered as it can affect the quality of the acoustic. When it comes to the size of the orchestra, it can be between 75-90 members but it could be smaller or larger depending on the work.
The orchestra though has four sections and they are the string section (the largest group), the woodwind section, brass section and the percussion section. There is the standard number of the instruments but they could be changed according to the conductor. Something could be added or removed.
There is the one called as the concertmaster who is seated at the first chair in the left side of the conductor. This is a violinist. The principal player is one that we should know.
The task is to guide each of their section in the orchestra. This person is the one who plays any solo act for their section of the instrument. There is an assistant to the principal player which acts as the substitute when the principal player cannot play. The section player is the ones who are all seated in the one section except in the place of the principal player or the assistant. Before they all begin a performance, they will have tuning.