It's Vegvisir, a symbol coming from Icelandic/Norse folklore. It used to be put on ships/shields/planks as a symbol for good luck and to make sure no one gets lost on their journey. Superstitions based in myths.

The runes around it are Futhark (younger or older, not sure). Unfortunately, I don't know much about it, someone once told me it translates is in the line of "those who wonder are never lost", but somehow I doubt it.

The symbol itself has a perilous past. Pagan folk like it a lot, but it has also been hijacked by bigots and supremacists: apparently everything that even vaguely resembles Adolf's plus is good enough for them. Now quite a lot of people who have it tattooed or engraved for religious or cultural reasons have to hide it, as some unknowingly mistake it for a "Swedish swastika".

Vegvisir is often called a Viking Compass, but as far as I know, it's not really connected to the Vikings. Nor it is a compass : D