A disciple is a person who follows and learns from someone else, usually a teacher or leader, in order to gain knowledge and skills.
For example, in a martial arts class, the students are disciples of their instructor, as they follow their instructions and learn from them to become better at martial arts.
Very Simple Definition:
A disciple is someone who learns from another person.
For example, when a child watches and copies their older sibling playing a musical instrument, they are being a disciple.