Two sides of one conversation
The character definition controls the AI role: name, greeting, personality and advanced details. The Persona controls your side: who you are and how the character should understand you. Both are visible to the model when it writes a reply.
What belongs in a Persona
Use a compact name, adult age when relevant, visual cues, role and relationship. Avoid a complete life history; official support estimates roughly 250 context tokens per Persona. Put world detail in a Lorebook and chat-specific events in memory.
What belongs in a character
Use the greeting to open a concrete scene and the definition to establish stable voice, goals and behavior. Save the draft as a private character rather than leaving it only on the device if you need it across browsers.
Diagnose a mismatch
Wrong pronouns or relationship roles usually point to Persona text. A character losing its voice points to the character definition or model. Forgotten plot facts point to context and memory. Fix the field that owns the information.