Parbase is just a component from which you extend to get some OOTB functionality.
If I can say in technical language, Parbase is a key component as it allows components to inherit attributes from other components, similar to subclasses in object oriented languages such as Java.
For example, when you open the /libs/foundation/components/text node in the CRX Explorer, you see that it has a property named sling:resourceSuperType, which references the parbase component. The parbase here defines tree scripts to render images, titles, and so on, so that all components subclassed from this parbase can use this script.
What AEM Version are on you using? IPArsys was used to make static templates have a common look and feel (for example - common components on all pages of the web site with the same data on each - like footer and headers).
IN AEM 6.4 - you should not be using that anymore for that purpose. You should be using Editable Templates and HTL. See this document for best practices for developing AEM Multi-page site: