The purpose of the study was to investigate how teachers teach to facilitate students' understanding of mathematical concepts. To answer our research question, the qualitative observation method was used on six different teachers who teach 4–6 in the subject of mathematics. The data collected from the study was processed through the thematic analysis which gave us results in the form of different categories. These categories are as follows: The teacher's use of the mathematical language, the teacher's use of aids during the lesson and the teacher's use of other words / synonyms. Through the study's previous research and theory, the socio-cultural perspective, we have analyzed the study's results. The results showed that the teachers who were observed used mostly the mathematical concepts in their teaching. They did this in the form of various aids, for example concrete material, the blackboard, the body language, digital aids.