In world war 1 the central powers were Germany, Austria-Hungary and the Ottoman empire. Italy was part of that alliance but because it switched sides before the name changed from the triple alliance to the central powers it is generally not considered a central power.
The Central Powers in WWI consisted of Austria-Hungary, Bulgaria, the German Empire and the Ottoman Empire. The Entente, Triple Entente or Allied Powers had as their major members: the Russian Empire, France, Italy, the US and the British Empire. Norway remained neutral throughout WWI.
because the entente powers were the countries against the Central power countries. the entente powers and the Central powers all had alliances against each other so then they all drew into war and declared war.