What is the physics meaning of the features in Matminer, such as "mean column"?

Hello,

I have imported composition-based features from Matminer following the steps in example “predicts bulk modulus of materials”. What is the physics meaning of the features, such as “MagpieData mean Column” and “MagpieData mode MendeleevNumber”? I can’t find them in Matminer documents. Thanks.