You are correct, in that the database consists of three datasets.
1. The apos_3011 is the unit processes. This will allow you to follow the inputs and outputs of materials, energy and chemicals from each process, but does not list the elementary flows or LCIA associated with the process, until it has been calculated.
2. The apos_lci_3011 is the life cycle inventory results. This is the unit process after it has been converted from unit processes into elementary flow inputs and outputs. It can provide you the LCIA results without calculating, but it does not show the inputs in terms of materials, energy, or chemicals.
3. The apos_regio_3011 provides regionalized emissions. Emissions in some areas have a higher effect than in others. E.g. emission of ammonia in Switzerland, compared to just emission of ammonia.
These are the differences between the three databases. They use the same scoping, so it is possible to import all three into the same database, and use them together. The LCI processes and non-LCI processes are good for different purposes.
I hope this makes sense, good luck.