Apple is a leader in consumer electronics, particularly smartphones, with its iPhone line. The company also has a growing services segment (including Apple Music, Apple TV+, and the App Store) that provides a steady stream of recurring revenue.
Microsoft is a diversified technology giant with a strong presence in software (Windows, Office), cloud computing (Azure), gaming (Xbox), and professional networking (LinkedIn).
Alphabet, the parent company of Google, dominates the search engine market and has a significant presence in digital advertising. It also has other growing businesses such as YouTube, Google Cloud, and various "Other Bets" (like Waymo and Verily).
Amazon is the leader in e-commerce and cloud computing (Amazon Web Services - AWS). The company is also expanding into areas like artificial intelligence, logistics, and physical retail.
NVIDIA is a leader in graphics processing units (GPUs) which are crucial for gaming, data centers, and AI applications. The company is also making strides in autonomous vehicles and high-performance computing.