Bus topology is a specific kind of network topology in which all of the various devices in the network are connected to a single cable or line. In general, the term refers to how various devices are set up in a network.
Techopedia explains it like that:
One way to think about a bus topology is that the line connected to all of the devices or nodes in the network is like an aisle along which a signal travels in order to find the node to which it is to be delivered. Typically, the cable in the bus topology has two end terminals that dampen the signal so that it does not keep moving from one end of the network to the other. Different types of bus topology can be referred to as linear or distributed bus topology. A linear bus topology implies that there is just one line associated with two distinct endpoints. In a distributed bus topology, there may be more than one linear pattern connected to the network. Bus topologies are often valued for their simplicity and lower cost of implementation. However, one drawback is that if the central line is compromised, the entire network will go down. Also, it can be difficult to troubleshoot these kinds of systems, and problems like data signal loss can occur with a longer linear cable.