Starting at a root node, and choosing Productions to determine later derivations that match the input.
Example
Given production rules:
 We can derive that
We can derive that S -> aabcde from following the root node and production choices

Starting at a root node, and choosing Productions to determine later derivations that match the input.
Given production rules:
 We can derive that
We can derive that S -> aabcde from following the root node and production choices
