What is neurodegeneration?

What actually is neurodegeneration? What are the major causes and where are we at with research?
Alzheimer’s disease (AD) is predicted to affect more than 135M people by 2050 yet there is currently no cure. Parkinson's disease (PD) is the second most common neurodegenerative disease also with no way of preventing disease progression.
This video will introduce what is currently known of these two diseases, provide a current explanation for causes of the disease and discuss areas currently being researched.

Timestamps;
00:00:44 Definition
00:01:22 Intro to AD and PD
00:03:52 Causes of neurodegenerative diseases
00:07:15 Where are we at with research?