The casacore package contains the core libraries of the old AIPS++/CASA package. This split was made to get a better separation of core libraries and applications. CASA is now built on top of Casacore.

The system consists of a set of layered libraries (packages) which can be seen best on the Modules page.
Included is a library (using Boost-Python) to convert the basic Casacore types (e.g., Array, Record) to and from python. Build of this library is optional.
This library is used in the package python-casacore (previously pyrap) that offers a high level Python binding to the Casacore functionality. The documentation of the python-casacore packages can be found here.

The main features of Casacore are:

casa package (libcasa_casa) : Core functionality and data types like Array and Record.
scimath package (libcasa_scimath) : N-dim functions with auto-differentiation and linear or non-linear fitting.
tables package (libcasa_tables) : Table data system supporting N-dim arrays with advanced querying.
measures package (libcasa_measures) : Values in astronomical reference frames using physical units (Quanta).
ms package (libcasa_ms) : MeasurementSets for storing data in the UV-domain.
images package (libcasa_images) : N-dim images in world coordinates with various analysis operations.

Casacore notes describe some parts of the system in more detail.

Casacore consists of the following subpackages:

casa	Core modules: N-dim arrays, quanta, OS, IO, HDF5, JSON, logging, and various other useful classes.
scimath	Mathematical modules N-dim functionals, linear/non-linear fitting, and miscellaneous.
tables	Database-like tables with advanced query language (TaQL).
measures	Quantities with references frames and their persistency.
lattices	Memory- or disk-based N-dim arrays (lattices) with masking, regions, expressions, and math.
fits	A C++ interface on top of cfitsio.
ms	The data format for visibility data as described in the MeasurementSet definition.
derivedmscal	Derived MeasurementSet quantities (like hourangle) that can be used as virtual table columns or as TaQL user defined functions.
meas	TaQL user defined functions to handle measures. It supports all conversions for epochs, positions, and directions.
msfits	Mapping of MeasurementSets to/from FITS.
coordinates	Coordinates for astronomical images.
images	N-dim images with masks, coordinates, and history.
python	N-dim python converters for basic Casacore data types.

Detailed build instructions are given on the casacore pages. It makes it possible to build selective parts of casacore.
When using a specific casacore package, it is useful to know the package dependencies when linking a program. They are as follows:

casa
scimath	casa
tables	casa
measures	tables scimath casa
lattices	tables scimath casa
fits	measures tables scimath casa cfitsio
ms	measures tables scimath casa
derivedmscal	measures tables scimath casa
meas	measures tables scimath casa
msfits	ms fits measures tables scimath casa cfitsio
coordinates	fits measures tables scimath casa wcslib cfitsio
images	lattices coordinates fits measures tables scimath casa mirlib wcslib cfitsio
python	casa boost-python python numpy

mirlib is distributed and built as part of Casacore. wcslib and cfitsio are external packages that have to be installed before building all of Casacore. Boost-Python is required when building libcasa_python.