To read a text and offer an assessment of the text's effectiveness along with suggestions for improvement.
The purpose of a critique is twofold.
First, it gives the author an experienced and unbiased assessment of the quality of their manuscript, its appropriateness for the target audience, whether it achieves the author's goals, and in some cases its commercial potential.
Second, it gives suggestions to improve any deficiencies noted in the assessment. These suggestions may address specific passages of text, or they may be more general in nature.
A critique differs from substantive editing because it includes assessment and general suggestions, whereas a substantive edit focusses on specific passages of text and does not include assessment.