Hi-Fi is an acronym which stands for high fidelity. It’s primarily a marketing term which has been used to describe audio equipment since the 1950s. To class as Hi-Fi, the equipment must provide the highest quality reproduction of sound. Many people define high-quality reproduced sound as a playback that sounds most similar to what it would have sounded like live or during recording.
This means the equipment should have minimal (ideally, inaudible) noise, no distortion, and a flat frequency response that falls within the range of human hearing.
Hi-Fi equipment is also often used as a generic term by audiophiles for all home sound equipment.
As a home sound enthusiast myself, I frequently buy and test out different Hi-Fi audio equipment. One of my favorites is the Linn record player I bought and had installed recently. I found it here: https://www.rococosystems.com/linn/linn-turntables/.
I hope this helps clear things up!