The group of people who believe in same religion and share common characteristics are Ethnic groups.
Explanation:
The group of people who share cultural ideas and beliefs that is a part of their community. The religious system shares their believes in god with a set of rituals.
Ethnicity are made up of beliefs, customs and traditions that belong to group of people. The five religious communities are Buddhism, Christianity, Islam, Judaism and others. Religion involves mostly about the devotional and ritual observances.