I'll introduce the segment of the special session on the Murchison Widefield Array (MWA) by giving an overview of this next generation low frequency interferometer. The MWA is the low frequency Precursor for the Square Kilometre Array; construction was completed in late 2012, science commissioning was completed in June, and the instrument has now entered its full science operations phase. The MWA is the first of the three SKA Precursors to be fully operational for science and will support four main science themes: 1) the search for signals related to the first luminous objects in the Universe, from the Epoch of Reionisation; 2) a wide range of galactic and extragalactic science based around wide-field surveys; 3) searches for common and exotic transient and variable phenomena on timescales from millisseconds to years; 4) studies of the Sun and the Earth's ionosphere. I'll describe the instrument, its capabilities, its operational parameters and an overview of the first round of successful observing proposals, initial results from the science commissioning phase, and the intimate connection between the MWA and the international SKA pre-construction phase that will be executed over the next three years. The full MWA system description is given by Tingay et al. (2013, PASA, 30, 7) and a full description of the MWA science themes is given by Bowman et al. (2013, PASA, 30, 31).