Sheaves and Algebraic Geometry

Consider the formula $$\operatorname{Proj}( \mathbb{C}[s,t]) \to \operatorname{Spec}( \mathbb{C}[s,t]) \colon \wp\mapsto \wp.$$ Recall that as a set, $\operatorname{Proj}( \mathbb{C}[s,t])$ contains all ideals $\wp$ of $\mathbb{C}[s,t]$ that are

• homogeneous (i.e. generated by homogeneous elements of $\mathbb{C}[s,t]$);
• prime; and
• that do not contain the irrelevant ideal $(s,t)$.