Electronics is the study of electric circuits and electrical components, and the design of useful devices. Some questions in this tag may be more appropriate for the [Electrical Engineering(http://electronics.stackexchange.com/) SE site.
Books and Introductory Kits
Many American Universities teach an introductory course in electronics based on the book The Art of Electronics and its accompanying Student Manual. The resulting course is lab-oriented. For physicists not affiliated with a university, Make Magazine's Electronics manual and the accompanying components kits (1,2) provides an easier way to purchase the necessary components, but the resulting curriculum is more electrical engineering oriented.