R&S and Security are the two different tracks of CCNA, the associate level certification offered by Cisco.

CCNA R&S deals with taking fundamental training on routing & switching and networking technologies used today. You learn about networking devices, networking technologies and how to implement networks(LAN) by using multiple technologies.

Whereas, In CCNA Security you learn how to secure your network using fundamental security technologies.

As you might know, Cisco has announced to consolidate it's all of the CCNA tracks into one and it will be known as CCNA from 24th of Feb, 2020. 

If you are about to take CCNA R&S/Security training, then I suggest joining Network Bulls and taking newly updated CCNA training. 

Check CCNA course training program at Network Bulls - https://www.networkbulls.com/training-ccna-course-delhi