Combine appearance with useful drainage observations.
Report visible leaves, plants in the channel or water passing over an edge. Say when the symptom began and include earlier clearance dates. A drip at a connection can relate to damage rather than debris, while an outside stain can have several explanations. Describe what you can see without testing the surface, opening fittings or climbing for a closer view. Treatment of a mark should not be assumed to repair the source of escaping water.
The fascia is the board along the roof edge; the soffit is beneath the overhang. A photograph can identify either without specialist terminology. Point out the marked area and any water problem separately so surface cleaning is not confused with debris inside the gutter.