Basic research seeks understanding of underlying phenomena without being directed at a particular practical application. Applied research instead starts from a specific practical objective. The distinction concerns the aim of the investigation: either kind can use experiments, observations and mathematical models.[ref]
Definitions of Research and Development by NCSES. I, Distribution by type of R&D; III.D, definitions used in surveys of federal research funding
For example, investigating how an unfamiliar material responds to light can seek a general explanation of its behaviour; optimizing a particular photodetector for a specified use has an application-driven goal. The first investigation can later enable useful technology without having started as a design project. Conversely, the practical aim of the second does not remove its need for careful measurement and a testable physical explanation. These categories describe research purposes, rather than a ranking of scientific quality.
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