Unix was popular because, originally, the source code was practically free. For various reasons the Unix license began to forbid the Universities from using the source code in their teaching. This lead Andy Tannenbaum to write MINIX which then inspired Linus Torvalds to write the Linux kernel for his Intel 386.
Unix has a long heritage and the new GNU/Linux has the luxury of learning from the success and failings of both Unix and MS-Windows. Of particular importance is the component-based architecture that facilitates the sharing of components among many applications. These are the focus of much modern development for GNU/Linux. Gnome, for example, uses Bonobo (built on top of the international CORBA standard) for its component architecture to support sharing.
CORBA is an object model defined by the Object Management Group. Its use by Bonobo is based on ORBit, a thin and fast implementation of the CORBA specification. Bonobo is then the Gnome architecture for creating reusable software components and compound documents. It was designed and implemented to support the needs of the free software community to facilitate component reuse and to allow new applications to build on the shoulders of those that went before them.
Don't be too concerned about the technicalities. You will see reference to these terms so it is wise to be aware of them. The details are not so important to the end user.