Is it near the tube? Is it on a bus route?

This is something you might say if you are trying to rent somewhere to live.

It = the flat / house.

The tube is only found in London. It means underground train (station).

In America you would say the subway, which in England means a tunnel under a road for pedestrians.

On a bus route. Do buses go past the flat?

This sentence is an example of houses, renting a flat, public transport.