Da capo is Italian for ‘from the beginning’. It’s used on a musical score to indicate that the musician (on reaching the point marked ‘da capo’) should go back to the beginning of the piece and start playing it again as a repeat.
Da capo is often shortened to ‘D.C.’ on a score and it is just one of the repeat terms and symbols used in music, to avoid having to produce lengthy scores that simply repeat the same sections.
Why is it called da capo?
In Western music, Italian is the language most often used to mark scores. This is because such markings/terms were first formally used by Italian composers before the practice spread across the rest of Europe (and other parts of the world), which then adopted the Italian terms. Standard terms indicating repeats, tempo and dynamics are typically taken from the Italian language.