ESAI stands for "Enhanced Strategic AI". It is an AI Commander Enhancement for Battlefield 2. It is a replacement for the default DICE commander script.
This is a screenshot of the base conditions used in the ESAI core. There are more complex conditions in the ESAI plugins. Editor used is notepad++.
A big thanks goes out to whomever made the BF2 syntax highlighting add on for np++ - I forget where I got it, but it is great for the type of work I'm doing.