Okay...this question comes to every young mind who are interested is space science or those who are familiar with space missions but are not professionals. On 22nd July of this year (2019) Chanrayan-2 was launched from Satish Dhawan Space Center, Sriharikota, India, and planned to reach the lunar orbit on 20th Aug 2019. The space probe will land on lunar surface on 7th Sept 2019 as planned. We know that first moon mission Luna-2 by Russia in 1959 had taken only 38 hours to reach to the lunar surface whereas Chandrayan-2 is taking around 47 days! So, where is the catch?
The average distance of moon from earth is 384,400 Km and if you follow shortest path with the speed of escape velocity of earth which is 11.2 Km/s, it would take only 9.5 hours to reach there. However, to reach moon escape velocity is not necessary because of smaller distance between earth and moon and therefore the moon missions are much longer than this time-frame. In case of Luna-2, a direct trajectory (direct trajectory is not always the shortest distance) was chosen and it took 1 day 14 hrs and 22 mins to crash land on moon's surface after it departed from earth on 12th September of 1959. A powerful rocket engine capable of producing a lift sufficient to cross escape velocity was used in Luna-2. At that time it was much costly mission and Russian Government had conducted this to beat America in Space War. Unlike Luna-2 mission, Chandrayan-2 is using a less powerful engine and therefore a direct trajectory can not be achieved. Instead, the rocket (GSLV Mark III) is taking Chandraya-2 space probe to a highly elliptical parking orbit around earth and then slowly increase the distance from earth by accelerating its speed in a number of small steps. When the distance will be sufficiently closer to moon, it will be sent to an orbit around moon. Now, by slowing down the speed the space probe will be slowly brought near to the surface of moon and when the desired landing location will be convenient to land on, it will directly jump on it. The complete procedure is quite complex to achieve but less costly. As ISRO is known to be a winner in this space age, nothing is difficult for it. Best of luck to ISRO...