Multiple Inheritance simply means that a class can inherit properties from more than one base class. In other words, a class can inherit from multiple parent classes -- it's not limited to just one.
Some prime examples of this are the file stream classes in the standard fstream library. In fact, every C++ stream class is derived from a common base class called ios. The classes we most frequently use are istream and ostream (using the common cin and cout objects, respectively). There is also another class called fstreambase, and this class contains member functions that have to do with file operations, such as open() and close() (for opening and closing files).
Here is how the ifstream and ofstream classes are declared:
class ifstream : public fstreambase, public istream { ..... }; class ofstream : public fstreambase, public ostream { ..... };
Notice that there are two classes listed after the colon, meaning that ofstream, for instance, inherits everything from both the fstreambase and ostream classes. It inherits all of its file operation functions from fstreambase. It inherits all of the output stream properties from ostream, which means that an ofstream object can do anything that cout can do. The same is true for the input stream classes.