Melody and accompaniment
This turbulent string quartet by Beethoven demonstrates the most common texture, that of a melody plus some accompanying chords or figures.
In this Bach hymn tune setting all the parts move in chords. This is called homophonic.
Music is only monophonic if there is just one part (if there are octaves as below it is not monophonic). Usually only short passages in a piece are monophonic but this example of religious plainchant from the Mediaeval period is all monophonic. You can have as many players or singers as you want on the same part so long as it is the only part.
Schubert’s violin sonata in D starts with the piano and violin playing together in octaves:
This Baroque trio sonata by Corelli starts with a polyphonic texture. The three string instruments (plus continuo) come in one by one, each imitating the opening entry.