In terms of airplane accommodations, coach means economy class. So practically, it's cheaper than private/first class and has more people in it. If you apply it to anything else, it probably means sharing something with a lot of other people for a not so expensive price.

It's difficult to know for sure without understanding the context where it was used, but I can think of two meanings: 1) Used literally, it means to travel to and from a destination in the low-cost seating (in the back of the airplane or bus). 2) Used figuratively, it could be used to describe an experience as frustrating or irritating. Example: "I just got off a two-hour phone call with my mother. Talking to her is like a round trip seat in coach!"

A trip by bus with others.

SIV (SEAT IN VEHICLE): This mode of transfer does pickups from your location like Airport and has drop offs along the way. Same applies for pickups from Hotel / Resort back to the destination like airport with pickups along the way.