How do nodes make money?

Could you kindly explain, in simple terms, how exactly do nodes earn their income? I'm particularly interested in understanding the mechanisms and processes involved in generating revenue for these critical components within the cryptocurrency ecosystem. Are there specific services they provide that enable them to generate profits? And how does this system ensure fair compensation for their contributions to maintaining the network's integrity and functionality? I'm looking for a comprehensive yet accessible overview that helps me grasp this complex concept. Thank you in advance for your assistance.