Demo classes means trial classes.

These are scheduled by different institutions to give a brief and to tell you about the entrance and other various exam related information and teach some basics.

It is an opportunity to check the surrounding and atmosphere of institute so that he can choose his next 2 years coaching teacher and place wisely.

Through this you can check whether you are interested in doing preparation and you are understanding the things. Good or not.

Good luck

There are various channels on you tube. You can see some topics explained by teacher.

Good luck