float3 The back axis.
Unity's back axis (0, 0, -1).
Matches <a href="/api/v1/web-embed/proxy?proxyUrl=https%3A%2F%2Fdocs.unity3d.com%2FScriptReference%2FVector3-back.html&mode=full">https://docs.unity3d.com/ScriptReference/Vector3-back.html</a>