Actually Grid is a type of distributed system (e.g. cloud and ASP are also subtypes of distributed systems),with some specific characteristics, for example:

- The nodes perform independent tasks (loose coupled nodes)

- They can be geographically dispersed

- They run batch jobs.

For details on the differences to cloud, have a look on this very nice paper which summarises them:

Cloud Computing and Grid Computing 360-Degree Compared

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4738445&tag=1

Grid computing system is a widely distributed resource for a common goal. It is Brother of Cloud Computing and Sister of Supercomputer. We can think the grid is a distributed system connected to a single network. This types of computing work with the large volume of files. Basically, it is a cluster types system. So people call it cluster computing.

Source: https://www.cloudwebhostingtips.com/grid-computing-vs-cloud-computing-supercomputer/

Grid computer tends to be more geographically disperse and heterogeneous by nature. Grid network also has various types. A single grid is like dedicated connection but a common grid perform multiple tasks.

The size of the grid is large. So grid computing is like supercomputing. It consists of many network, computer, and middleware. Grid computer is dedicated to some specific function of the large volume of data. In the grid process, each task divided into a various process. All the process starts execution simultaneously on a different computer. As a result, very few seconds needs to execute and enjoy the flavor of supercomputing.

For more:https://www.cloudwebhostingtips.com/