Within one note there is a blend of frequencies present. The nature of the blend determines what we hear and how we describe that tone. If there is no recurring pattern to the frequencies present, ie no one frequency dominates, then we hear the sound as a flurry of vibrations, or noise. If there is only one steady frequency present, we have a pure tone. If there is a single sound with several frequencies present , we can usually hear a plurality of frequencies but we assign a pitch to the dominant one.
Strings fit that description.
When we hear a blend of frequencies we assign a tonal description to the sound. If there are lots of high frequencies present we say the sound is bright. If there are fewer high frequencies present we say the sound is more mellow, rounded, smoother etc. In a sound with multiple frequencies present, the different frequencies are called partials . The lowest is called the fundamental and that is the one we usually identify as the pitch of the note.