At the end of the day, the only way to get cash into a bank account is to no longer own the (full amount of) shares.
Its not the only way.
The simple and cheap way is to own shares and keep them. You might get a dividend payment every so often.
With shares in a single company, there is a risk that the share price could up or down. You can change how much you are exposed to those risks. One way is to sell some of your shares. You could also buy more.
You can also use futures contracts, and spread betting to do the same thing. These are not simple, and might not be cheap. If you get your sums wrong, and you can lose lots of money. You can also use them to reduce the risk of big losses and gains.
For example, you could agree to sell your shares in 3 months time but only if they have doubled the current value again. You would be paid a little bit of money right now, which you would keep if the share price hasn't doubled by then. If the share price triples, then you sell your shares, but you have lost out the extra increase in value.
Doing this sort of thing doesn't make much sense if you've only got a small amount invested, as the transaction costs are likely to be more than the amounts that you would gain or lose. However, its a way to adjust your exposure to a risk - if you either need income right now, without selling the shares - or if you want to guarantee that you won't lose more than a certain amount.
Betting gets a bad name, and if you have an addictive personality, its worth avoiding altogether. Betting doesn't have to be bad though, in the same way that buying house insurance is like placing a bet with an insurance company that your house will burn down.