This is a new word in talent development circles, but there really isn't anything groundbreaking about it. Borrowed from marketing, an omnichannel approach means you are creating a seamless experience for your customers through every channel or device. The idea is to meet your customers in as many platforms as possible—in a physical store, online, on a mobile device, and possibly in an app.
Within e-learning, the process has started with blended learning, combining traditional classroom experience with online learning, but it has hit a snag. At its core, the omnichannel approach cuts out the binaries within e-learning—online and offline—and challenges developers to expand their scope.
For example, learners could sign up for an online course. They could start the course on their computer and then continue the course on a mobile app during their lunchbreak. From there, maybe they want to start an online tutoring session, and that may then lead to in-person learning.
These media must all be linked, because users will want to turn to them at any given point in the process, depending on their needs. However, they must also optimize the capabilities of each platform. Don't have your mobile app look like a website tab; play to what a user would expect to see from that medium.
Blended learning was a solid starting point, but learners won't wait forever for you to optimize their experience.