Net neutrality is, in a nutshell, unhindered traffic (and speed) to all parts of the internet. This prevents big business and ISPs from filtering or slowing down particular sites on the internet. Without this we could be charged more for streaming content or blocked from accessing certain sites entirely.
This might be Recently the Supreme Court heard a petition from the FCC to undo Net Neutrality and ruled to uphold Net Neutrality rules in full! Way to go Supreme Court!
Here is a video explaining net neutrality in more detail.