Koala is intended for compiling CSS preprocessors, like SASS, Less, Compass Framework, Dust and Coffee Script. The benefits of using preprocessors are that it allows extending CSS to support implementing functions and inheritance as well as reusing definitions. This way, your code becomes more compact and you save a lot of time and effort. However, a browser cannot readily "understand" preprocessor code, and this is when an application like Koala comes in handy as it can compile preprocessor code into standard code.
There are various advantages of using Koala. For instance, you can set a sort of "watch folder", which means that every time there is a change, the application can automatically compile the code. Moreover, it can compress code automatically immediately after the compilation has been completed.
Regrettably, Koala is no longer among the best applications of its type, which even its developer alerts. Due to changes in the development method, the product has become obsolete. However, this does not mean it cannot be still helpful. In such a case, it is good to know that it is open-source.