The diversity of characteristics is something that cannot be separated from students. Concept understanding is a process that has many benefits and dynamic nature. Researchers assess the understanding of mathematical concepts that students master is still relatively low. mastery of other skills is needed that can support the needs of students in understanding the concepts being studied. The CORE learning model is one of the innovative learning models designed to improve students' understanding of mathematical concepts. The method used in this study is a quantitative method with a quasi-experimental design. From the calculation results obtained from the validity and reliability of the data have a valid value and normal distribution. For normality and homogeneity tests, all items are normal and homogeneous. It is known that the results of the t-test hypothesis in the experimental class have an average value (mean) of 63.7 post-test and pre-test of 47.5, the increase in the average result is known to be 16.2 for all test results. From the results above, it can be concluded that the use of the CORE learning model with the student facilitator and explaining strategy can improve understanding of mathematical concepts and student learning activities.

Keywords: CORE learning model and Student Facilitator and Explaining Strategy, Understanding Mathematical concepts, student learning activities