There are several ways to ask about your job in English.
These all mean, "What is the name of your company?"
Where do you work? What company do you work for? Who do you work for?
Your response: I work for (insert company name). This is typically used when you work in an office or the headquarters of a company. "I work for Microsoft."
People generally say "I work at _____" when they work at a local chain, retail, or franchise location. For example, "I work at McDonald's" or "I work at Starbucks."
These all mean, "What is your job title?"
What do you do (there)? What position do you hold? What do you do for a living?
Your response: I'm a/an (insert job title).
Jim: Hi. My name is Jim. Tom: Hi Jim. I'm Tom. Nice to meet you. Jim: Nice to meet you, too. Where are you from? Tom: I'm fro m Canada. What about you? Jim: I'm from Texas. Are you in town visiting family? Tom: No, I'm here on business. Jim: Oh, ok. What do you do? Tom: I'm an IT specialist. Jim: That sounds interesting. What company do you work for? Tom: I work for IntoTech. What about you? Where do you work? Jim: I'm in sales. I work for Mouse Global, Inc. Tom: Wow. That's a big company.