Over on YouTube Rob from Frugal Radio has uploaded his latest video which explains RF filters in a concise and easy to understand way. RF filters are often used together with SDRs to block out strong interfering signals which can degrade reception at other frequencies.
In the video Rob goes over the different types of RF filters such as high pass, low pass, band pass and band stop, and shows a few SDRs that have filter banks built in.
Filters 101 : Improving reception with your SDR or radio - a look at RF filters