The Emergency Liquidity Assistance (ELA) are temporary loans provided by the Eurozone's National Central Banks (NCBs) to banks in their jurisdiction. These loans are outside of those provided by the ECB, such as the LTRO program. The idea was to allow for some discretion for the NCBs to help their domestic institutions in a crisis situation that is specific to that nation, as opposed to a Eurozone-wide issue managed by the ECB. Unlike the ECB's lending programs where the risk is shared by the Euro-system, the NCBs bear the risk on ELA loans. The ECB can in fact stop the NCBs from providing specific ELA assistance if it is deemed to interfere with the ECB's overall policy actions.
With the massive LTRO lending program by the ECB, one would expect that the Eurozone banks would repay their ELA loans and roll them into the ECB's 3-year loans. That seems to be what in fact happened for some nations such as Belgium, but the roll was only partial for Ireland. The Central Bank of Ireland still has some €45 bn of ELA loans outstanding.
This is an important development to watch because it indicates continuing stress in the Irish banking system - with some banks so tapped out, they don't have enough ECB-eligible collateral. It also poses a risk to the Central Bank of Ireland that is not shared by the Eurozone (for now), particularly given that Ireland is in no position to bail out its central bank.