請問這句話中"centre" and "centre-left"分別指的是什麼?

題目：

請問這句話中"centre" and "centre-left"分別指的是什麼?
整段話如下："What is remarkable in this gathering is that you have parties here traditionally from the centre and centre-left,developed and developing countries,in one voice saying that the world economy needs a positive outcome soon on the Doha Development Round."

解答：

正黨和左派