Graphical Evaluation and Review Technique (GERT) is a network analysis technique used in project management that allows probabilistic treatment both network logic and estimation of activity duration.
The technique was first described in 1966 by Dr. Alan B. Pritsker of Purdue University and WW Happ.
Development in GERT includes Q-GERTS - allowing the user to consider queuing within the system.
The nodes are used to connect activities, but also to determine type and conditions of relations between them.
There are also two types of relations that concern activities outcoming from the node: It's much less popular than PERT (Program Evaluation and Review Technique) or CPM (Critical Path Method) however, it allows some of those methods limitations to be addressed.