Any mobile phone that is not a smartphone.
Feature phones have proprietary operating system (OS) firmware. If they support third-party software, it is only via a relatively limited platform such as Java or BREW.
Compared to software for smartphones, Java or BREW software for feature phones is often less powerful, less integrated with other features of the phone, and less integrated into the main user interface of the phone.
This is changing, as newer versions of Java and BREW allow software to be more powerful and integrate with more features of the phone, although the difference is still present, especially on the interface side. While third-party smartphone software is a "first-class citizen" on the phone, third-party Java or BREW software is usually restricted to a special "applications" section of the interface.