Presently most libraries are facing some common problems related to:

Increasing number of records and items 
Large number of members to be managed
Less budget for proprietary solution
Lack of sufficient staffing
Lack of powerful administration over all modules in Library
Lack of standards to be followed

So Koha (an open source software) overcome all these issues by providing different customized modules and full control over all the functionalities. In addition, it supports characteristics like


Stable - Even under extreme load
Robust - Capable of handling a high volume of
Flexible - Accomodate the varied needs of libraries.
Secure - Protect our patrons' privacy and data.
User-friendly - Facilitate patron and staff use of the system.
Freely licensed - Open source software.