Complex sentence: The "European Council" (a separate institution from the Council) is composed of the Prime Ministers or executive Presidents of the member states, and appoints the Commissioners and the board of the European Central Bank.
Split into simpler sentences: The "European Council" (rather than the Council, made up of different government Ministers) is composed of the Prime Ministers or executive Presidents of the member states. It appoints the Commissioners and the board of the European Central Bank.