Modeling software (or modelling software in UK English) is a computer program to build simulations or other models.
Modeling software relies on a modeling language, that “ is any artificial language that can be used to express information or knowledge or systems in a structure that is defined by a consistent set of rules. The rules are used for interpretation of the meaning of components in the structure. A modeling language can be graphical or textual.” 
Modeling languages can be used by instructional designers/technologists or even teachers to produce teaching materials (e.g. simulations). Learners also can be engaged into modeling activities.
2 Types of modeling software
This an incomplete inventory for now. See Wikipedia:Model for an overview of what a model could be and follow links ...
- Most microworlds allow both teachers and students to build models. See microworlds and Programming microworld.
2.2 Mathematical systems simulation
2.3 Special simulation software
- Network configuration
- molecular modeling (HyperChem, Spartan, CAChe, PC Model, etc.)
- Mechanical dynamics
- Climate modeling, e.g. EdGCM
- Business processes
- Production chain modeling.
2.4 3D Modeling
- All sorts of 3D CAD programs (Solidworks, Rhinoceros, Autodesk AutoCAD, 123D, TinkerCad, etc.)
- General purpose 3D modeling software
- 3D programs specialized to build models for 3D environments (virtual reality, computer games, etc.