Put simply, a 'global issue' is an idea or theme presented in your text/s that has significance in the world. The IB states that it should have the following properties:
It has significance on a wide/large scale
It is transnational
Its impact is felt in everyday local contexts
An example of a global issue might be:
Money as a source of social repression in Metamorphosis and Death of a Salesman
This issue focuses on a specific topic, is not too broad and would allow for interesting development in the oral.
.