People talk about Legal Theory and I do not understand what it is. The Theory Part.
In Physics, Chemisty, Geology, Economy, Sociology... Theory is an explanation of a phenomenon( why it occurs and numbers and variables are permitted it is often the case that a Theory is highly quantitative). A theoretic scientist deals with ideas, concepts and tries to explain the observations. An experimental scientist is the one that provides the theoretic one with the observations
In Computer Science, Philosophy, Languages... Theory is an explanation of how the phenomenon occurs, i.e how to produce it.