Abreast means side by side and facing the same direction. When soldiers march abreast, they walk in a line next to each other rather than in single file. When two cyclists ride abreast on a bike path, they're pedaling alongside each other, which can sometimes block the path for others trying to pass.

The word also means keeping up with current information or developments. When you stay abreast of world news, you're keeping yourself informed about what's happening. A scientist stays abreast of new research in her field by reading journals and attending conferences. A basketball coach keeps abreast of his players' progress by watching their performance in practice.

Think of the physical meaning as the foundation: just as two people walking abreast stay level with each other, staying abreast of information means keeping level with the latest developments and not falling behind. When your teacher tells you to stay abreast of your assignments, she means you should keep up with the work as it comes, staying even with the class rather than lagging behind.