As internet usage increase web application development become a challenge, because it is mostly customer requirement that web application must be usable on both desktop computer and mobile.
Suppose you are developing an application for biosciences institution that needs samples of different trees plants, soil and animals etc. For this the user of this application needs camera connectivity promptly, sometimes it is required to transfer data to other users located nearby with data transfer size not more than megabits. Also mostly user requires traveling on distant unknown places to collect required sample data. Along With this there are other users working at offices. These must be capable of viewing, validating the data and then generate results against it. Now for all these requirements to meet you have two techniques either create a responsive web based application which will work on both web and mobile or create two separate applications one for web and one for mobile where database is common for both.