When light can't go through something, it either bounces off or is absorbed. So how can light be stopped if it just finds another place to go? The process is called electromagnetically induced transparency (EIT) and was first used to stop light in 2001.
It's pretty complicated, but essentially scientists are able to take a crystal that usually doesn't allow any light to pass through it and manipulate it to let a specific frequency of light through, albeit slowly. If they stop altering the crystal while there's light inside of it, that light becomes trapped or frozen in the material.
This can only last for a limited time, however. The time light can be trapped and still hold the same information (e.g. An image) is only fractions of a second. Only through even more manipulations of the crystal and environment can scientists expand this time. The provided source has a much more detailed explanation of this all if you're so inclined.
Recently, a group of scientists managed to trap light for a full minute! This came pretty close to the predicted maximum amount of time that particular material could hold light, but there are other materials that may allow for longer durations.
This may not seem relevant to the real world, but harnessing light will have numerous applications. Quantum computers will be exponentially faster than current computers and communication networks that utilize quantum mechanics will also be faster.
