Model Based Testing
Is just another testing concept. it's mainly built around the idea of using the models which describe a system to produce test cases to test the system. in UML we can look at a system's statecharts diagram to generate test cases that will guarantee state coverage for example. or even other coverage criteria. another example is use case based testing, which uses the use case model to generate high level user acceptance test cases.
Test modeling describes an approach to model the overall testing activity of a system. specifically the testing system could be considered a seperate system of the testable system. and then it can be modeled through structural, behaviour and implementaion diagrams. in a nutshell test modeling is all about descibing testing concepts of a system as models that go hand in hand with the system under test models.