Niantic has added a new feature called Routes to Pokémon GO but it is not fully active for most players yet to create their own route. Creating a new Route will slowly be activated for more players as time goes on.

Discover the world in an all-new way with Routes!

Explore the globe with the Pokémon GO community as your guide! Chart a course to show off your favorite sights, or follow in the footsteps of local Trainers to see what that community loves.

Routes are created by adventurous Trainers, just like yourself! Imagine what you’ll find as you travel another Trainer’s Route—an encounter with your favorite Pokémon? A new friend to share Raid Battles with? Follow a Route and find out!

Make a Route

1. Choose a PokéStop or Gym to be your starting point.
2. Hit record to begin mapping your Route.
3. Fill out some info about your Route, then submit it for review.
4. Once accepted, Trainers can follow your Route!

Exploring a Route

1. Check the Route tab from the Nearby menu to see local Routes.
2. Choose one that catches your eye.
3. Follow the Route and enjoy exploring!

Zygarde Cells

• Keep an eye out while you’re exploring a Route—you might come across a Zygarde Cell!
• Zygarde Cells are the components that make up Zygarde, the Order Pokémon. You can collect Zygarde Cells in your Zygarde Cube and use these cells to change Zygarde’s form.
• Encounter Zygarde in the Special Research story “From A to Zygarde”!

Bonuses for exploring Routes

What’s an adventure without some treasure? There’s an assortment of bonuses to enjoy while exploring Routes!

: Follow a Route to its end for the first time to earn a new Route Badge.
: Earn Buddy Candy more quickly.
: Pokémon will be more attracted to Incense when you’re exploring a Route for the first time.
: Earn an XP bonus for the first Route you complete each day. After completing Routes for seven days, you’ll receive an increased XP bonus.
: Earn a Buddy Heart when you complete a Route while adventuring with your buddy!

Source: https://pokemongolive.com/en/routes