When you embark on something, you are starting it — and it's exciting. You might embark on a new career or embark on a trip to the Galapagos Islands. You wouldn't embark on a trip to the grocery store.
The verb embark can be used specifically to refer to boarding a ship for a journey. When used for general travel, the verb embark often implies a longer journey: "She embarked on a trip around the world." Besides physical journeys, embark can be used to mean to start other kinds of journeys as well. You might embark on a spiritual journey or embark on the path to enlightenment. Pack well.