In mid-2017, the Ethereum community was caught in the throes of an acrimonious debate over how to best scale the network. At the center of this debate was a proposed upgrade to the network called Ethereum Meta (or Metropolis), which would have implemented a number of changes aimed at making Ethereum more scalable and user-friendly.
Unfortunately, the Metropolis upgrade was never completed. The primary reason for this is that, in the months leading up to the planned upgrade, it became clear that there was significant disagreement within the community over which changes should be included as part of Metropolis.
This disagreement eventually led to a hard fork of the Ethereum network, with a new version of Ethereum (Ethereum Classic) being created that retained the original functionality of the network.
Since then, development on Ethereum Meta has effectively ceased, with all focus shifted to the new Ethereum network. It remains to be seen if any of the proposed changes from Metropolis will ever be implemented, but for now it seems that this upgrade is nothing more than a historical footnote.