On the simplest level, a highpass filter is just a filter (sometimes called a low-cut) that attenuates low frequencies below a certain cutoff frequency and allows frequencies above to pass.

What is a high pass equivalent to?

Section 1 is a high pass, which is equivalent to a grade 5.

What does a high pass do?

An audio high pass filter (HPF) is an equalization tool that attenuates all frequencies below a set point. In other words, high pass filters remove low frequencies while allowing high frequencies to pass through. They are used in almost every application of audio technology.