It was dark on the street but I remember what the thief looked like.

looked 是动词 look 的过去式，表示"看起来、显得"。 like 在这里是介词，表示"像...的样子"。 looked like 是一个固定搭配，意思是"看起来像..."或"长...的样子"，用来描述外貌特征。