\__name__ is the name of the module. 
```python
print(__name__)
```
Will print the name of the module: ie what you would import. So if you are given a python program that looks like this:
```python
import some_module
print(some_module.__name__)
```
The output: some_module

The special case is when a module is run directly then the name is \__main__ meaning it is the main module.

This line of code checks to see if the module is being imported or run, and only runs if it is beign run. It basically was to clean up sphinx output because sphinx was importing it to do the documentation and then running all the tests. 

The reason importing would run all the tests is that modules run all code in them that is not ina  function on import. Now when sphinx imports tester it won't run the tests because
```python
if __name__ == '__main__':
```
will stop any code from running when the module is imported.