Translation:That bus is small.
その それ そちら そう そこ These pronouns are used to describe things that are closer to the listener.
Note that they can also be used to describe the things that is previously mentioned. This is where the "the" comes into play.
For example, 毎日バスで学校に行きます。そのバスは小さいです。 I go to school by bus everyday. The bus is small.
In this case the bus is referring to the one that is known to both the speaker and the listener.
If you go through some exercises in the JP -> EN course, most of the sentences with "the" are translated to その
As I have explained above, その is not just physically "that there," it is also from a conversational view "that thing just talked about." This is exactly the usage of "the" in English.
There's a difference in idiom between Japanese and English: imagine that you and a stranger are waiting for the bus, as it pulls in towards the bus stop, you say this sentence.
In English, the most natural form is "the bus", but in Japanese it is going to be この or その (or possibly あの if it's still some distance away from both of you).