The children took out building blocks from the playbox and started constructing.

playbox 是由 play（玩耍）和 box（箱子）组成的复合名词，字面意思是"玩耍用的箱子"，即"玩具箱"。这种构词方式在英语中很常见，通过将两个简单名词组合来表达更具体的物品。