It symbolises peace, closeness and warmth, but also protection and security, trust, satisfaction and love.
In the pendant, the gilded circle is a symbol for the sun (the male) while the sickle stands for the moon (the female). They are surrounded by the ring (the universe). Everything seems to be in harmony and peace. It could also symbolize a ship with a round sail - sailing calmly through the world.
It's up to the imagination of the viewer - the meaning of peace and quiet, harmony and security is the important thing. It's essential for a trusting satisfaction in life.