I hear many guitar player saying that the sound of this electric guitar is very 'muddy' . I am a beginner. What does muddy means?
It can mean a number of things, but the result can generally be summarised as your playing sounds not clear enough.
Lack of treble brilliance is one factor, but not necessarily the most important. What I call a muddy sound is usually caused by too many low-ish pitched notes sounding together in an uncontrolled fashion. This is best adressed by
- Having a clear concept of what you actually want to play. Don't play notes that don't really fit in a chord, especially not open bass strings. Jazzy variations can also be culprits.
- Make sure that only the notes you deliberately play actually sound. Guitar strings aren't isolated systems like the tone generators of a synthesizer; if you simply leave them open they may ring even though you've never actually played them. Always watch out carefully for such “rogue sympathetic vibrations” and make sure you properly stop strings that sound in unintended ways.
Similarly, make sure you stop notes after their intended duration is over (typically after each chord change).
- Make sure the notes you do want to play actually come out well-audibly. Good technique and dynamics go a long way here. Listen to your playing and take care that important melodic notes really come out, whereas accompaniment is often better subdued. Palm mute is useful so you can give notes a distinct loud attack without causing an indistinct muddle of cross-ringing notes. Also, make sure you play well in time and with good intonation.
- Sound also factors into this, though I'd argue equipment is less critical than playing technique. But a muffled high-impedance humbucker makes it much harder to bring out the right notes than a twangy Tele singlecoil. And in particular, distortion can quickly make an utter mess out of an only slightly muddy clean signal. So, keep the gain down when playing more chordal stuff, and treble up especially when doing delicate arpeggios etc..
OTOH, sympathetic resonances can actually sound quite good on acoustic guitar, giving a nice “wide-open space” sensation. And be sure to actually know the sound. Always listen carefully to how the end result sounds, and if you want a high-gain sound on stage you should at least occasionally also practice with distortion.