All objects (except for vector objects, e.g objects created using the drawing tools, such as rectangles or ovals) in your Document has a shape and some content, for example a Text area or Story frame where the text is the content. Or, an image with a placeholder as the shape, and the actual image as the content.
You can specify to enable a shape to change size vertically and horizontally to fit the content. When resize of the shape is enabled, blue icons represent the maximum shrink value, and red icons represent the max growth value. Red icons represent unlimited shrink/growth.