Here we introduce the prefixed perfective for "to go(walk)" — пойти́. It is a perfective verb with a focus on "setting out" somewhere, just like other verbs of motion with «по-» («пое́хать», «побежа́ть», «полете́ть», «пове́сти»).
It is completely normal to use «идти» when talking about public transportation, i.e. passenger vehicles that repeatedly follow a prescribed route. These are preferred when talking about routes. Typically, it is идти because we treat it more like an objective fact of a certain trip taking you somewhere than a particular vehicle going to a certain place (almost as if «идти» is not used as a verb of motion but as a way of stating the destination). «Ходить» is also used: for example, when saying that a bus exists that takes you from one place to another.
When arriving at a terminal station on a subway, you can hear the following:
A personal vehicle will always use ехать/ездить.
A reminder: you use ONE-WAY verbs when describing motion in one direction, even if repeated. The verbs cease being interchangeable when the context of repeated motion implies the "trip back" cannot be included (like "After school I go to the station and take a train home."— here you have a sequence that makes the return trip absurd). We rarely have such sentences in the course. In real life, just remember to occasionally take a step back and refresh the basic idea behind the opposition: one-way motion vs. multi-directional trip.