E-learning means learning via a computer, tablet, or phone. It is also written as eLearning. It can be anything from a short video with a quiz to a longer program with several courses and a certificate at the end.
The advantage of e-learning is that it can be taken whenever it fits. Everyone gets the same explanation, and it is easy to see who has completed it. The downside is that a bad course just gets clicked through. That is why learning design matters: short pages, clear learning objectives, and a quiz that checks what matters most.
E-learning works best together with what happens in everyday work. A course can, for example, prepare for a meeting, follow up on classroom training, or provide a reflection to bring to one's manager.