Ask for some questions

1.  Main.py : "  gcn.train(train_data,test_data )"  What are the "train_data" and the "test_data"?  

2. train.py :" model = model_func(placeholders, size_u, size_v, self.latent_factor_num)"(line 43)    What's the "self.latent_factor_num"?