'Gamma' and 'ion' sound like contents of a physics textbook. But here, we are looking at a symbol with an even deeper meaning than metaphysics.
The Gammadion Cross is formed by group of four Greek letter gamma (Γ), the capitalised third letter of the Greek alphabet. In a Christian context, 'three' is a reminder of the Trinity, and each gamma represents one of the four Evangelists, who radiate from the central Greek Cross, which represents Christ.
The most common is the Swastika Cross but other arrangements exist, such as the cross shown on the right. This is a Voided Cross and similar to the relatively recent Thugsta Cross)
Alternative names include Gamma Cross and Gammata Cross.