Node is Discrete or Continuous

The node dialog box has a selector:  with the values Continuous and Discrete, which allows you to choose whether the node represents a continuous or a discrete variable.

It is common to have a continuous variable that you want to break up into intervals so that you can treat it as a discrete variable, which is known as discretizing the variable.  If the variable is truly continuous, it is usually best to make it a continuous node, and then discretize it with an interval list, rather than just making it a discrete node.  This provides better documentation of the node, and makes it easier if at a later time you want to discretize it another way (i.e. with a different number of states, or different cutoff points for the state intervals).  Also, that way it can accept continuous values when learning from cases, or generate them when simulating cases.

Alternately, a discrete node may have numeric quantities attached to each state, so that each state can represent a number, but the variable is incapable of representing numbers between those of each state. More Info.

Note:  Utility nodes must be continuous and decision nodes must be discrete.