Chat, not a script
Who starts the conversation
In Agents you called start with a question. The run ended when the answer printed.
In a bot the user writes first in Telegram or Slack. The process keeps running and answers each message.
Agents page vs Bot page
Developers who import Agent in their own program use the Agents story.
Teams who want replies inside an existing chat use Bot. The instructions can be the same.
Reference: documentation