You can be a software tester in many kinds of organisation, from a big tech brand that creates consumer products, to a large multinational organisation focused on business applications, to a smaller consulting firm that works on a contract basis, perhaps for the government, on health, education or defence projects.
Software is used in many different situations, on our mobiles phones, desktop computers, to run machinery, gather data, and to design things. It’s relied upon by individuals and businesses who use software to work properly to complete what they need to do.