This question uses the term "Travis Brick", but I've never heard it before. What is it, and where does the term come from?
The Travis Brick is the 1×1 brick with studs on four sides.
The nickname arose amongst LEGO Space builders. It was nicknamed The Travis after talented Space builder Travis Kunce. He liked the part so much he had a tattoo of it.
The brick is especially useful in SNOT techniques as it has studs on all but the bottom surface.