Online abbreviations are shortened forms of words or phrases commonly used in digital communication. They help save time and space, making messages quicker to type and easier to read. Examples include LOL for "laugh out loud," BRB for "be right back," and IMO for "in my opinion." These abbreviations are especially popular in social media, texting, and online gaming, where fast communication is essential. While they can enhance efficiency, it's important to use them appropriately, as not everyone may understand the same abbreviations, leading to potential miscommunication.