In severe cases, the viral infection causes a high fever, bleeding into the skin, and necrosis (death) of cells in the kidney and liver. The damage done to the liver from the virus results in severe jaundice which yellows the skin. Hence, the yellow in yellow fever..
filter definition: The definition of a filter is something that separates solids from liquids, or eliminates impurities, or allows only certain things to pass through. (noun) A Brita that you attach to your water faucet to remove impurities from you...
A high pass filter is a filter which passes high-frequency signals and blocks, or impedes, low-frequency signals. In other words, high-frequency signals go through much easier and low-frequency signals have a much harder getting through, which is why it's a high pass filter.