Display problems are visible, which makes them easier to describe than most laptop faults — provided you know which details to note.
Lines across the display
Note whether the lines are vertical or horizontal, whether they are coloured, and whether they change when you move the lid. Lines that appear or disappear with lid movement suggest the display cable or hinge area, while fixed lines more often relate to the panel itself.
Flickering
Flickering can be constant, or it can appear only at certain brightness levels or refresh settings. Check whether it happens from the moment the laptop starts or only after some time of use.
Dark patches and spots
Dark or discoloured areas that spread over time usually indicate physical panel damage, often from pressure on the lid or from something being carried on top of the closed laptop in a bag.
Completely blank screen
If the laptop appears to run but shows nothing, check for a faint image in a dark room. Connecting an external monitor also tells you a lot: if the external display works normally, the fault is likely in the panel, cable or backlight rather than the system.
Cracks
A cracked panel should be handled carefully. Avoid closing and opening the lid repeatedly, and do not press on the cracked area.
Getting a display problem checked
Photographs of the screen, taken with the laptop running, help significantly. Attach them or describe them when you make your enquiry.