What do you understand by software maintenance? what are the diferent types of maintenance?

Software maintenance refers to the modification of a software product after delivery, in order to rectify faults, or it can also be its up gradation in order to improve its performance and make it more effective.

There can be many angles to look at software maintenance from. It can be from the point of view of fixing bugs, that is, the maintenance and repair of errors. Another aspect of maintenance is to make changes in accordance with the changes in technology and the changing requirements of the operating scenario.