Probability / Randomness
We see there is a lot of misunderstanding and misconception regarding the term Random and how it is used on DelugeRPG.
There are a lot of places in the game where randomness is used to bring some uncertainty in the game. These include deciding what pokemon will show up on the map next, what its level will be; What attack a gym leader's pokemon will use against you, etc.
Here's a simple example of how we use probabilities. Say there is a 2% chance of your next wild pokemon being a legendary pokemon. We let the computer pick a random number from 1 to 100. The computer does not favour one number over another, so it is pretty fair. If the number the computer picked is equal to or lower than 2, we let the pokemon be a legendary pokemon. When you move again, this process is repeated. The probability remains the same and so does the range of numbers it chooses from.
The misunderstanding comes from people believing that you will find exactly 2 legendary pokemon if you move 100 steps (using the 2% from the previous example). While this sounds about right, this doesn't always happen. You may find 4 legendaries in 100 or you may find none. This is because the computer's pick is really random. Its previous choices do not affect its next choice. While the 2% will hold true over a large number of steps (say 1,000,000), it will not seem that way when seeing a small number of steps. This is the same reason why fair coin tosses will not have a heads,tails,heads,tails,.... sequence but rather have heads and tails bunched together even though each side has a 50% chance.
This is also why a raffle event such as LEGENDS++ (now discontinued) may sometimes seem uneffective. It may increase the 2% chance of a legendary to 4%, but it does not however guarantee you a large number of legendary pokemon during the time that it is active.
Useful LinksProbability (English Wikipedia) Probability (Simple Wikipedia)
Randomness (English Wikipedia) Randomness (Simple Wikipedia)
Misconceptions about Randomness