This article explains two formats that use the ASL file extension. It also explains how to open both formats on a computer.
How to create MAC system information and log files (asl).m4v
A file with the ASL file extension is an Adobe Photoshop style file. They are useful when you want to apply the same look to multiple objects or layers, such as a certain color overlay, gradient, shadow, or other effect.
Because a single ASL file can contain one or more Photoshop styles, they are useful not only for backing up your own styles, but also for sharing styles with others so they can import them into Photoshop for their own projects.
There are even websites that host free ASL files for you to download. Just do a quick search on the internet for "download free ASL files" and you'll find a bunch, like FreePSDFiles.net.