The Jolly Roger is a flag with a skull and crossbones that was traditionally flown on a pirate ship, although many pirates would just fly a plain black flag.
The reason pirates wanted people to know they were pirates was just to frighten the crew of other ships into giving up without a fight.
The Jolly Roger in the picture is being flown along with some other modern flags.
A journey is a trip from one place to another, usually taken over quite a long time. The word journey can also be used to describe progress from one state to another, for example a weight loss journey. The people in the picture are on a bike journey.
A similar word to journey is travel or trek.