Final answer:
In a Karel world, the horizontal pathways are called streets, which, along with avenues (the vertical pathways), make up the grid-like structure that dictates movement in the programming and robotics environment.
Step-by-step explanation:
The horizontal pathways in a Karel world are called streets. Similar to a city grid, these pathways dictate how walkers, drivers, or in the case of Karel the robot, can navigate the environment. In a Karel world, the streets and avenues define the two-dimensional grid on which Karel can move. While a street is the horizontal route that Karel can traverse, an avenue is the vertical counterpart. This setup helps teach students the basics of computer programming and robotics movement within a grid-like environment.