1 Perhaps the most important distinction is between neurons with and neurons without long axons. 2  The long-axoned cells, called principal neurons, transmit information over long distances from one brain region to another (Sheperd,1979). 3  Principal neurons provide the pathways of communication within the nervous system.
Training is the process of being conditioned or taught to do something, or is the process of learning and being conditioned. When you teach a new employee how the business works, this is an example of training.
In many areas of information science, finding predictive relationships from data is a very important task. Initial discovery of relationships is usually done with a training set while a test set and validation set are used for evaluating whether the discovered relationships hold. More formally, a training set is a set of data used to discover potentially predictive relationships. A test set is a set of data used to assess the strength and utility of a predictive relationship. Test and training sets are used in intelligent systems, machine learning, genetic programming and statistics.