difference between gazebo pose and odometry/filtered pose

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When I click on the bot inside the Gazebo world, I see that there is an option to change the pose of the robot.

What is the difference between this pose and the pose published by the ekf_localization_node on the odometry/filtered topic?

I ask this because I need a way to ascertain whether the pose being published on odometry/filtered (by ekf_localization_node) is correct or not i.e whether or not the bot is being correctly localized in the odom frame.