" That one's easy, kiddo. He's riding the synchronicity freeway, and so everything just falls into place; time, movement, even distance just sit up and beg for him. You're having an adventure, kiddo. If you survive it, it'll be fun."- Boston Brand explaining the Synchronicity Freeway to Timothy Hunter
Synchronicity Wave Travelling is an instictual ability employed by John Constantine. Powers that only the people with the title "The Laughing Magician" can use. (The Roots of Coincidence) Synchronicity is the experience of two or more events that do not share a direct relationship but have a related means alter or it is also seen as a set of causal unrelated "Coincidence". Synchronicity in magic, is the belief the universe is guiding you. These random events and (un)pleasant coincidences is the universe leading you somewhere.
By stepping in the synchronicity freeway, he takes control of synchronicity, John can make his own luck and advantages in battle. This allows him to use fate and synchronicity to his advantage, putting fate in his side and multiplying his chances of succeeding even more. Easy to say, synchronicity wave travel allows John to make his own luck, and reshape the battle he's fighting to his own accord and liking. (Hellblazer issue 247, 274, and 176)
This lets him do things such as locating someone and winning at gambling games. In battles it lets him do feats such protection from danger and harm, bullets and casted spells to miss their marks, escape and evade enemies, using synchronicity to slow or weaken his enemies down, and meeting the right kind of people and being in the right place at the right time. This is one of the key factors why John wins against all odds, and be named one of the most powerful magician alive (The Laughing Magician ).
This ability is powerful enough to affect even God and Satan. Though powerful, it is not permanent and will loose its effects once he steps out of the synchronicity wave. This ability doesn't grant Constantine an automatic win, but it does give him nigh-invincibility as long as he rides the synchronicity wave. The synchronicity only benifits and protects John, but not other people.
The Laughing Magician
A title given to John Constantine and his late brother. Laughing magician existed during the growth of mankind. They are people who rebuked gods whom other people worship. Some even managing to destroy or use gods for their own whim. Only people with this title can do a synchronicity wave travelling and unlock its full potential. By becoming the Laughing Magician, the person unlocks all synchronicity powers including warping reality, fate, and destiny with godlike feats. Constantine seldomly uses his title and its powers, but his late brother has used this power to literally control Constantine's lives and those he loved.