The scope and purpose of application comprehension is much broader than that of program comprehension. Application comprehension can be viewed as a spectrum spanning the gamut comprising code-level understanding at one end (low level) and understanding the architecture of interorganizational systems at the other end (high level). The nature and the depth of knowledge sought through application comprehension is directly related to the purpose at hand. In this paper, we propose a unified conceptual framework for application comprehension. The framework is influenced by Bloom's taxonomy. The proposed framework considers several aspects of application comprehension and draws upon our experience in developing large-scale, multi-tier distributed applications for brokerage and financial services. We discuss how the proposed conceptual framework can be implemented by leveraging the sophisticated tools that are available as open-source software. We conclude the paper by indicating how the proposed framework can be used to learn software engineering principles, tools, and practices in education and training contexts.