I have a vague understanding of those notions but not much more.
As I understand it, roughly, both a filter bubble and an echo chamber reinforce your own belief system by reducing exposure to different opinions. But the filter bubble results from an algorithm (example: social media), while the echo chamber is made of free voluntary choices (example: forum).
But is it really that simple ?
For example, I know algorithm usually means a set of computer instructions and that it is this meaning that comes with the “filter bubble” concept. But, in a certain way, medicine, psychology and sociology also have some “rules” and concepts that show that there is, sometimes, also certain “biological” algorithms and “psychological” algorithms (if you can call them that). It seems we are not completely free to join or contribute to an echo chamber.
On the opposite, on a social media, reinforcements of our own belief system also occurs with voluntary choices to exclude “friends” who disagree too much and invite “friends” who share closer viewpoints (at least for now).
And on top of that, some serious newspapers use filter bubble for every internet-based channels: forums, social media, chat, etc.