Training
   - One key to machine learning is training.
 
   - The system is presented with a corpus (a bunch of
       examples).
 
   - It uses the corpus to learn the domain.
 
   - It can then be used to give answers.
 
   - These are usually for new examples, but can be for the old ones.
 
   - Systems can also continously learn; so they can constantly learn,
       and interact with the input and output.
 
   - They can learn from failure.