Learning by Interacting
"Interacting" within the absorbing, doing, interaction, reflection framework means interacting with others, rather than interacting with a object. For example, discussing a problem with others rather than operating a forklift.
Although we can learn by reading and listening, real depth of understanding (knowledge) happens when the learner expresses the new learning herself, either through discussions or writings. That is, the learner needs to encode the learning herself, rather than simply receive what others have encoded — she needs to verbalize when watching, hearing, or performing new tasks. Verbalizing is a powerful concept (Marzano, 1998). This is one of the reasons that interacting with others can be such a powerful learning tool — we are not only get the benefit of verbalizing, but also receiving immediate feedback.
The physicist Freeman Dyson wrote that when writing, he closes the door, but when doing science, he leaves it open — "up to a point you welcome being interrupted because it is only by interacting with other people that you get anything interesting done." These interactions are often useful in creating the aha moment -- the joining of one's knowledge with another bit of knowledge, information, or data. Knowledge is not normally created out of nothing, rather one gains knowledge by being able to "connect" two or more pieces of data, information, or knowledge together. Thus knowledge is a process of understanding (gain meaning) by connecting.
References
Marzano, Robert J. (1998). A Theory-Based Meta-Analysis of Research on Instruction. Mid-continent Aurora, Colorado: Regional Educational Laboratory: http://www.mcrel.org/PDF/Instruction/5982RR_InstructionMeta_Analysis.pdf