SURFACE 'LEVEL', DETAILS or FEATURES
The surface details of a text refers to the straightforward meanings that do not require interpretation to be revealed. For your essays, you do need to comment briefly on the surface meanings of a text (indeed it's a good way to open an essay: 'On the surface this poem/play/story is about...') but then go on to analyse the more interesting and important implied or 'deeper' levels of meanings (click here for more) and messages.
For GCSE, you are not only expected to interpret the language of the texts you study, you also need to show how you arrived at such an interpretation. This is done by quoting from the text and commenting on the language of the quotation to show how it led you to your interpretation.