Of these four nouns the one that confuses English learners most is definitely travel.
Travel is used to refer to the activity of travelling in general. In this meaning it’s always uncountable, i.e. takes no article and is always singular.
His job involves a great deal of travel.
Her interests are history, art and travel.
Travel can be plural when it means journeys, especially abroad.
On their travels they met lots of interesting people, many of whom became their lifelong friends.
Travel is also often used as a modifier before other nouns.
She works as a travel agent.
I never go on holiday without a travel iron.
Travel insurance is worth taking out – it’s inexpensive and can save you a lot of money and hassle if you get in trouble while on holiday.
When talking about a particular occasion when someone travels somewhere, use a journey or a trip.
There’s a difference in meaning between the two: a journey is an occasion when you travel from A to B, especially over a long distance, whereas a trip means going from A to B and back to A together with the reason for it, be it pleasure or business.
Next month they’re going on a journey to India.
My journey to work usually takes about an hour.
Two winters ago we went on a skiing trip to Andorra.
He never went on school trips because his parents didn’t have the money.
And lastly, a voyage is a long journey in a ship or spacecraft.
The Titanic sank on her maiden voyage (=first voyage).