These were perhaps the first two technologies that set the concept of Web2.0 on fire. RSS is more or less, a way to provide a website's 'table of contents', so that you click on any of the headings and get taken to the corresponding 'chapter'. They allow ways to take the links to the content out of the original site's context into your own, at your convenience. Wikis are largely text-based centralized spaces where a communities can get together and share their interests.
However the point of this blog post is, now matter how I try to explain it, it is still incomprehensible to many people. So ... here are two video's that illustrate these concepts in a much more entertaining and engaging way. Enjoy!
RSS in Plain English
Wiki's in Plain English