Sapera is built to run both a single store and an entire chain with several stores and several sets of accounts. That is why there are several levels on which you can organise data.
The organisation (the chain) — the top level that ties everything together.
Store / department — the individual physical or organisational unit. If you have only one store, this is simply your single level.
Accounts — the financial track that postings and reports belong to. An organisation can have one or more sets of accounts.
The levels determine how data is kept separate and added together. For example they control:
which figures roll up to the whole chain, and which belong to the individual store,
how sales and purchases are allocated to the correct set of accounts,
who can see and work with what.
Even with a single store it is worth knowing the structure, because it makes it easy to grow later without having to rebuild.
You manage the units under Organisational units.