You're asking for the job description in a single sentence. I can do that, but since "chat" relates to a few distinct roles, I'll give you the most common one:
A Chat Support Specialist is responsible for providing real-time customer service and resolving inquiries efficiently through online text-based platforms while managing multiple conversations simultaneously.
If you were referring to the people who build and train the AI for chatbots, that would be:
A Conversational AI Designer is responsible for designing, scripting, and training the logic and content of automated chatbots to ensure accurate and human-like interactions.
Which of these two roles is closer to what you had in mind?