The Classical era in music was (roughly) between the years 1750 to 1830.
Some of the most famous composers of this era are: W.A. Mozart, Franz Schubert, Joseph Haydn, Muzio Clementi and early L.V. Beethoven. Women composers were very rare during this time, but some examples are Marianna Martinesand Hélène-Antoinette-Marie de Nervo de Montgeroult.
New instruments which appeared during the Classical era were the piano and the clarinet.
The Classical symphony orchestra usually comprised a small string section (violins, violas, cellos and double bass), woodwind (flute, possibly clarinet, oboe and bassoon), plus trumpet and horn. Timpani are also sometimes used. The overall number of players in an orchestra was smaller than during the later Romantic era.
In the Classical era, the texture of music is generally less “complicated” than in the Baroque era. Music of the Classical era tends to sound light, clear and elegant. Instead of being mostly polyphonic, at this time music was mostly homophonic. Homophonic (which literally means “sounding together”) usually means there is a single melody which has an accompaniment based on chords or arpeggios.
Classical music usually has a few, limited performance directions, such as basic dynamics and articulations. Piano pedalling is not usually marked, as pedals were not developed until near the end of the Classical era.
Here is part of Mozart’s Clarinet Quintet (for clarinet and string quartet). Notice how the melody is almost completely in the clarinet part, with the strings providing a light accompaniment.