It is the practice of looking into a suitable medium to detect important messages or visions.

The media most commonly used in Scrying are reflective, refractive, translucent, or luminescent surfaces or objects such as crystals, stones of glass, various shapes such as crystal balls, mirrors, reflective black surfaces such as obsidian, water surfaces, fire or smoke but there is no particular limitation on the preferences or prejudices of the scryer; some may stare into pitch dark, clear sky, clouds, shadows, or light patterns against walls, ceilings, or pond beds. Some prefer glowing coals or shimmering mirages; some close their eyes, notionally staring at the insides of their eyelids, and speak of "eyelid scrying". They can be a powerful tool for divination, but if you're a beginner, there are a few things you need to know.

The word "scrying" actually comes from the Old English word descry, which means "to make out dimly" or "to reveal." Therefore, Scrying is about revealing the unseen through our in-born second sight. Second sight is our capacity to see things that can't usually be perceived through our five senses. Scrying is an ancient practice that goes back thousands of years and is found in all cultures worldwide. Techniques for divining the past, present and future are used. This means there are numerous techniques and methods available for use today.

References:

1. Scrying - Wikipedia. https://en.wikipedia.org/wiki/Scrying

2. .Scrying: How to Practice the Ancient Art of Second Sight ... - LonerWolf. https://lonerwolf.com/scrying/

3. .Scrying Divination Magic Beginners Need To Know. https://www.thepeculiarbrunette.com/scrying