Basically you plug it into the mains supply available to you, at home or in the studio or at a gig venue, and then plug all your electric gear into the post power filter/stabiliser socket.
The device is designed to protect all your gear from either power surge or fall-oot, giving you, for example, a steady 220 V with no variation as always happens with normal power socket feeds.
The device also filters all those nasty hums, fizzes, frizzles and unwanted frequency disturbances typically caused by anything drawing power from the same wiring circuit as the one you are using.
In a house this could be a radio or the ‘fridge or even an automatic light switch going on and off outside the entrance to the front door.(I have experienced both these problems; first in a home studio and second, amazingly, in a recording studio).
There are multiple possible sources of this unwanted noise traffic in the wiring, and all these noises, if not filtered out, are of course amplified when they pass through effect pedal(s) and/or amps.
OK, this is sometimes cool and I admit to having used these noises several times when recording film and theatre music.
But I have also had to spend a couple of hours in a recording studio once trying to find out why, at random moments, a strange metallic crrrr! sound would go through my pedal board and emerge from my speakers with octave, flange, echo and reverb effects enhancing its unwanted presence. It turned out that my un-filtered power source was picking up a signal from the air conditioning in the studio control cabin each time it sprung into life. So we turned off the aircon completely and solved the problem.
The engineer gave me a lot of stick for not having my “gear sorted” despite my best efforts to defend my set up.
A guitarist I play with often uses a vintage Fender Champ, with a great sound but a lot of background noise. After modding the Champ he still had quite a lot of noise so he bought a power filter/stabiliser which he inserts between his gear and the wall socket he is using in the rehearsal room or at gigs and the noise problem has virtually disappeared.
One example of a power filter/stabiliser is the Furman P-1400 AR E:
“Furman P-1400 AR E Power Stabiliser/Conditioner - 6A max, stabilises power (174-264V), greatly reduces line noise, features Furman’s Linear Filtering Technology (LiFT), 10x IEC outlets (rear) & 1x (front), large blue digital LED display, main power switch (front), BNC socket for optional gooseneck lamp. Dimensions: 19”/1U (depth: 305mm). Weight: 7kg”
It is somewhat expensive(!) but there are others on the market. I know that the one Werner Broos from The Golden Dawn now uses cost him around 230 EUR.
I hope you find this some help…and no, I have not bought one yet. It is on my list but first I have a couple more EHX effects I want to buy!