What does it mean that workers in other countries are less productive?
When it is said that workers in other countries are less productive, it is because they are typically lacking in capital, education, and technology. If the goal of each country is to dig a hole, then those with less backhoes, shovels and hands (aka capital) will not be as advanced. If citizens are uneducated and cannot read a manual, then a backhoe is no good to them and they are stuck with shovels and their hands. Finally, the quality of their capital (aka technology) matters, because you would rather have 1 backhoe than 5000 shovels.