Randomness is a concept used (and less formally) in mathematics to imply that there is no way to accurately predict an event (to know what will happen before it takes place) or to sense a trend. Anything that is randomly selected for no conscious purpose can be assumed to be simply by chance factor. An illustration of an occurrence random event is a financial windfall, a lottery win. A computer can generate lists of seemingly random numbers. It is difficult for humans to do the same, since the brain functions in patterns.
If someone is asked to keep repeating heads or tails at random, a considerate human observer or a reasonably programmed computer may eventually tell which one the person is likely to say next because the computer recognizes the patterns. The user can click on Random Page on a website such as English Wikipedia to get a random article. The odds of being on anyone's webpage are the same as on every other webpage.