Capital Expenditure - upfront costs for buying physical equipment like servers and data centers that you own. Like purchasing a house instead of renting.
Before cloud computing, companies spent millions in CapEx buying servers, storage, and networking equipment for their own data centers.
CapEx (capital expenditure) is a finance/accounting concept, not a cloud service. In cloud adoption discussions, it contrasts with OpEx (operating expense): buying and owning hardware/data centers upfront (CapEx) versus paying for cloud usage over time (OpEx).