The French horn was created with of a long, spiral tube ending in a flaring bell, three valves, and a funnel-shaped mouthpiece. That is why is called a "horn" as many musicians playing classical music call this instrument.. One f the ironic things with the French horns is that there are not strictly French in origin.
The horn (is a brass instrument Modern French horns have three valves which lower the pitch a semitone, a tone, and three semitones (minor third). It became known in England about this time, and they called it the French horn. Use of the term French horn dates at least from the 17th century. Another major contribution in the 18th century was the emergence of the French horn as an orchestral instrument. The French horn produces a beautiful sound but is one of the trickiest Western classical instruments to play.
If you are a musician you will understand the differences of a French horn with other instruments
As I mention before it is usually higher than twelve feet (for a single horn in the key of F) of mostly conical tubing (like you will find in a classic tuba or euphonium), wrapped into a compact, coiled form with a flared bell. A very important characteristic of the French horn is the fact it was a very defined resonances up to the 22nd or beyond, playable up to at least the sixteen harmonic, compared to about nine playable resonances for the trumpet and trombone.
The horn plays in a well high portion of its cousins in the same musical family as compared to most brass instruments. Another characteristic feature is the funnel-shaped mouthpiece, unlike the cup-shaped mouthpieces of other brass instruments. It also allows the instrument to produce resonant highs out to about 1500 Hz, compared to low 750 Hz without hand closure. The valves divert the air through gentle and small extra lengths of tubing, thus making the instrument shortly longer and therefore deeper.
The problem with the French horn is how difficult it is to play, and that's why so many people simply don't even play such an amazing instrument. The French horn isn't the easiest of instruments to start playing, and based on this fact it's uncommon to see young people to start playing the instrument until they are at least 11 or 12 years old. Also for young people it is never easy to tune the horn, because its tuning is adjusted by slides and the instrument is tuned with the hand in the bell.
A true pity, there is nothing like the music of a good French horn.