THREEFOLD LAW -- The Threefold Law is not technically a law per se. It is more of a defining principle that governs many pagans and wiccans. It is similar to karma. Basically what it means is that whatever you send out be it magic workings or whatever will come back on you three times as powerful.
When or how it comes back to the person depends on which variation is believed. There are several different thoughts on this from cosmic to the more mundane.
Not all use magic practitioners use this principle. Just like with any religion, there are differences in beliefs in Paganism and Wicca.
TRIPLE GODDESS -- There are many triple goddesses in ancient pantheons. The Moirai, the Morrígna, and the Norns are a few of them. These are three individuals that form a group function. Then there are those with three heads like Hecate at the three-way crossroads.
The Wiccan Triple Goddess is represented by the phases of the moon and are visualized as three different stages of life: Maiden, Mother, and Crone.
There is debate as to whether She is a reincarnation of an older goddess/es or a creation of the Neopagan revival.
Thor was the protector of humans and gods against evil. He carried the hammer Mjollnir. He was one of the most popular of that pantheon. When the church started to take over, the people began to wear Thor's hammer in defiance.
Jupiter governed over the distribution of laws and used oracles to give the people his will.
TUESDAY -- Tuesday is named for the Norse god Tyr, which relates to the Germanic god, Tiu (Twia). The Romans called it dies Martis, which translates to Mars day.
Both Tiu and Mars were gods of war, while Tyr is a defender god.
Tyr, in Norse mythology, was shown to bear only one hand. The other was sacrificed in the jaws of Fenrir when the gods tricked the wolf son of Loki into chains.
Disclaimer: None of these pictures belong to me. I found them on Google.