What were the major features of Johnson's Great Society?

The main feature of President Johnson's Great Society was a push to eliminate poverty.

Johnson attempted to do this in a number of ways.  He attempted to do this through education, providing Head Start programs for disadvantaged children who were too young for school and creating the work-study program to help college students.  He attempted to do this through job training programs like the Job Corps.  He attempted to do this by creating the Medicaid program that would allow poor people access to good health care.  Finally, he attempted to do this with the Community Action Program, which gave money to poor communities to improve themselves.

In all of these ways, Johnson was attempting to end poverty.  This was the main feature of the Great Society

What were the implications of Johnson's "Great Society"?

I would say that one of the most profound implications of Johnson's "Great Society" was that it was the last time people saw government as a positive agent of change.  Johnson believed that government programs could help make people's lives better and the public accepted that point of view.  Whatever else one wishes to say about the Great Society, its view of governmental action was a pinnacle moment in American History.  After Johnson, government action was never to be seen in the same light again.  Johnson took a broad view towards government action and the ideas that government, as opposed to private industry, was the source of assistance to people was something that was not to be seen again and not seen since.  Johnson's own experiences convinced him that if problems existed in society, it was up to government to solve them and to bring some level of remedy into people's lives.  The time period was one in which people accepted this.  Such a wide role of government action is no longer seen in American politics without significant blowback.  The recent health care debate was historic in how it reached back into this particular idea, something that Johnson himself would have embraced as a part of the "Great Society."  Yet, the amount of negative feedback regarding "socialized medicine" or "intrusive government" represents a reality that Johnson himself would have never experienced to such a degree.  In the end, the "Great Society" is one of the last triumphant moments where American liberalism was recognized.  It can be said with a tinge of melancholy that government has not been viewed in the same light since.