"In the constructivist perspective, knowledge is constructed by the individual through his interactions with his environment.
How we perceive knowledge and the process of coming to know provides the basis for educational practice. If we believe that learners passively receive information then priority in instruction will be on knowledge transmission. If, on the other hand, we believe that learners actively construct knowledge in their attempts to make sense of their world, then learning will likely emphasize the development of meaning and understanding."
(Constructivism: from Philosophy to Practice)

What constructivist teaching might look like: from Wikipedia

Basic definitions of constructivism:

Another definition and example introducing constructivism:

Constructing knowledge in the classroom overview:

Diagram of constructivism for visual learners :)

Connectivism--How technology plays a role in changing views

Example of designing a constructivist type of lesson:

Details about areas that need addressing in constructivist learning: