There are actually a lot of ways that you can make extra money online. How well the different methods work for you will depend on how much time you have to spend on them and what skills you have as well as how much effort you want to put in.
If you just want something easy and flexible to earn some money then survey sites can be good. These send your regular surveys to answer and will pay you if you complete them. There are a lot of sites that offer this and the amount that they pay will vary. Some will send you a lot of surveys and some will just send a few so it can be a good idea to find out more about the different survey sites first. Then you will be able to find one that has a survey frequency that suits you and the amount of time you have available to do them.
There are other things that you can do if you want short jobs that are flexible. Some people choose to view videos, do small tasks, enter competitions or play free lotteries to see if they can make money that way. If you have the time, doing a combination of different things can help to get more money as well as to keep things more interesting.
If you have skills that you would like to use then freelancing can be a good way to do so. There are websites where you can look for freelance work and these will allow you to be easily matched to those that are looking for the skills that you have. These jobs are likely to pay more than the smaller jobs but they will take more time and effort. They will still be unlikely to pay as much as a regular job because you have to compete with people from all over the world and many will be prepared to do the work for a low amount of money. Therefore you will need to show that you have the skills that they are looking for and that you are worth paying a good salary to. You may be happy to be paid a bit less money anyway if you are able to work comfortably in your own home and at a time that suits you.
Some people make money by selling things online. There are lots of places that you can sell things, such as online auctions and marketplaces, social media pages and classifieds. Whether you have items that you owned and wish to sell on or are buying items to sell on, then these could be good options for you to sell them through. It is always wise to take a look and see what sorts of things they already have for sale to make sure that your items will be right for the site and that there are not too many there to compete with. Make sure you research before you buy any stock to sell.