Alternative media's aims are often to challenge existing powers, represent groups that have been marginalized, and foster links among people with like interests. 
Alternative media is also known as independent media; it differentiates itself from the mainstream media (commercial, publicly supported or government-owned) by content, aesthetics, production, distribution, and audience relations.
Alternative media often has a different set of values, objectives and frameworks, which allows them to provide an alternative viewpoint: information or interpretations of the world not normally found in the mainstream media.
Source: Alternative Media. Wikipedia. Image source: Ivan M V. Perspective of Banos de Dona Maria de Padilla. CC BY-SA 2.0. Wikimedia Commons.