A sample shows you the tile's real colour, finish and texture in your own home and lighting, which a screen can't do. Look at it at different times of day and next to your paint, worktops or furniture.
Bear in mind that a sample is one small piece. Tiles can vary, especially wood, stone, marble or handmade designs, and your order may come from a different batch from your sample. Check the product photos too, to see the full range of variation across a floor or wall.