Qiskit is a software development kit for writing quantum computing experiments, programs, and applications.

This is a simple meta-package to install the elements of Qiskit altogether.

The best way of installing qiskit is using pip:

$ pip install qiskit

Prior to version 0.7, both Terra and Aer elements lived together under the qiskit package. In 0.7 we split qiskit into qiskit-terra and qiskit-aer.

The Terra element is the foundation of Qiskit and allows you to write quantum circuits with our Python API and run them using the built-in simulators provided with the package. Aer element is a collection of native simulators designed to be fast and full-featured.

If you don't need/want these simulators, you can always install qiskit-terra in isolation by doing:

$ pip install qiskit-terra

The meta-package started with version 0.7 to respect the continuity of qiskit versions. The Terra element did the same to provide continuity with its own history.

Considering semver, the Qiskit meta-package pins the minor version number of each Qiskit element to get new patches automatically.

Nevertheless, upon changes minor or major version numbers of the elements, the meta-package version must be updated according to the following rules:

1. If a dependency increased the major number, increase the major number of the meta-package.
2. Else:
   1. If a dependency increased the minor number, increase the minor number of the meta-package.

If you want to contribute with one of the Qiskit elements, refer to their individual sites:

• Terra on GitHub