Subject headings are keywords, or "tags" that librarians give to a title. Unlike ordinary keywords, subject headings describe what the book is about in a consistent way by gathering all the random terms used to describe a topic in natural language, and connecting them to an official subject heading.
Learning and using the subject headings for your field of study can give much more focused and relevant results. See below for some tips on using subject headings for research in Architecture and Urban Design.
Architecture -- [place name, style, time period]
The subject heading "Architecture" will find works on the design and style of structures. Works on the process of construction are entered under "Building". General works on structures or edifices are entered under "Buildings". This heading can be subdivided by place for works on architecture indigenous to the place named, e.g. Architecture--United States, or time period, e.g. Architecture, modern -- 21st century. To search a specific style format the subject heading style first, e.g. Art deco (Architecture).
Other useful subject headings:
Architectural Design -- history
Urban design and planning theory are interdisciplinary fields covered by a wide range of subject headings depending on your focus. Subject headings and keywords can be combined for best results. Some examples of subject useful headings: