Swarm robots are classified into two types:

• Homogeneous swarm robots
• Heterogeneous swarm robots

Homogeneous swarm robots are those that are a collection of robots of the same kind and type, such as a group of mobile robots (as shown in the following photograph). They replicate a biological species' behavior to perform a task.

The following photograph shows a group of robots that are trying to maneuver over rough terrain:

Heterogeneous swarm robots are those that are a mere collection of robots working together to perform an application's code. That's it? Yes, although, to be a bit more precise, they are a collection of robots of varied kinds. This is quite the trend in robotics nowadays. In areas such as geographical inspections, a drone and mobile robot combination is used to perform mapping and the analysis of a certain environment. In manufacturing industries, mobile robots and static robot arms are used to work in parallel for machine tending applications such as loading or unloading workpieces. In warehouses, drones and automated guided vehicles are used for the inspection and loading of materials onto racks.

There are applications called multi-robot system applications that shouldn't be confused with swarm robotics. The difference here is that the robots would communicate with other robots in the system autonomously, but work independently. If one of the robots in the system breaks down, the other robots may not be able to carry out the task of the specific broken-down robot and hence would bring the application to a standstill unless the problem was looked into.

Let's look at how multiple robots can communicate in ROS.