It'll feature a protected front, top, and rear, but the sides will be open for His Holiness to see the throngs of people gathering for him.
For hundreds of years, Popes were transported in horse-drawn carriages or sometimes carried in an enclosed chair by footmen, but His Holiness finally traded for some real horsepower in 1929. While his ride sometimes varied depending on the country being visited, a Mercedes-Benz was generally the common choice. However, the Pontiffs have ridden in everything from a modified GMC Sierra to a Ferrari Mondial over the past few decades.
Pope Francis has definitely preferred more plebeian transportation, though, including a Renault 4 running on biofuel. A trip to South Korea even put him in a Kia Soul, and he opted for an Isuzu D-Max in the Philippines.
The Post's whole list is quite a fun read, and it's fascinating to see how the Popemobiles evolve over time.