There are 14 Trophies that can be collected.

Bronze

Threshold
Cross the broken bridge without completely rebuilding it.

Mirage
Find the hidden desert flower.

Explore
Discover all cloth creatures in the desert.

Adventure
Pass through 15 gates while surfing through the sunken city.

Trials
Sneak through the underground passage without tearing your scarf.

Ancestors
Find a mysterious creature hidden in the temple.

History
Uncover all 10 ancient glyphs.

Crossing
Reach the summit with a companion and return to the beginning.

Rebirth
Finish the game and return to the beginning.

Reflection
Sit and meditate with another player for more than 20 seconds.

Return
Start the journey again after a week long break.

Silver

Companion
Finish the game with the same partner for the majority of the journey and return to the beginning.

Wonder
Meet 10 or more unique travellers.

Gold

Transcendence
Collect all unique glowing symbols across one or more journeys.

http://www.ps3trophies.com/forums/playstation-trophy-news/11635-journey-trophy-list.html