There have been many discussions, research-based or opinion-based, with regard to the definition of active learning that it has transformed into one of the "household" verbiage in education. Some educational professionals think that active learning is defined as a process of engaging students or learners to achieve the different levels of learning (i.e. as per Bloom's Taxonomy). For example, being in an "active learning" classroom would demonstrate lessons that are being delivered in a more student-centered instruction rather than a teacher-centered instruction. This would also mean that students are collaborating with each other (i.e. small groups, by pairs) and developing meaningful connections through the facilitation of the teacher. Likewise, the expectation from students is to go beyond being the receivers of instruction. Rather, they are to evolve into being effective and relevant producers (i.e. creating apps, providing solutions to existing problems, having foresight to develop future solutions and ideas, being able to work with colleagues interdependently, being able to adapt in different environments, having the initiative to find solutions and to get through barriers and challenges). For this reason, students will be able to develop higher order thinking, critical and analytical skills, problem solving skills, meaningful collaboration, and consistent desire to learn, to name a few.
As part of understanding the different facets of active learning, many have connected blended learning with active learning. If you are to ask me if both are the same, I will say that we all have a slight difference in our perspectives and understanding of the two. Personally, both have similarities, and yet, some will argue that one is a component of the other. However, I don't think that this should be the sole or primary contention. Instead, we should focus on how active learning can be implemented using a variety of styles, including blended learning, project-based learning, problem-based learning, personalized learning, and the like.
Below is an example of a Blended Learning Infographic from http://elearninginfographics.com/blended-learning-k12-classrooms-infographic/ that can help explain how teachers are using technology in a K-12 blended learning environment: