Rapport is a process and can be defined as a recognition of and willingness to communicate and share values with others. . 

In other words rapport is getting on well with another person, or group of people, by having things in common; this makes the communication process easier and usually more effective. 
When you develop the skills to create powerful rapport with people, you can’t help but feel powerful.

Rapport is a state of harmonious understanding with another individual or group that enables greater and easier communication
 
Rapport can be built by using number of techniques such as matching your body language and maintaining appropriate eye contact.