The Filter Builder app is included in DSP System Toolbox. You can find it, along with the rest of the apps for your installed products, by clicking the Apps tab in the MATLAB Toolstrip.
The Filter Builder app builds filters. It relies on the fdesign object-oriented filter design paradigm, and is intended to reduce development time during the filter design process.
Specifications help you find the best algorithm for the desired response. The workflow includes choosing the constraints and specifications of the filterto use as a starting point in the design. Postponing the choice of algorithm for the filter allows the best design method to be determined automatically, based upon the desired performance criteria.
Apps are interactive MATLAB programs you can use without writing any code. Most toolboxes come with apps, and you can download more for free from the MATLAB File Exchange. You can also package and share your own apps.