For our purposes, novelty just means new. So how do you show the patent office that you have created something new? There are basically three ways this can be accomplished. One way is to show a physical difference from all preexisting inventions. If the invention in question is an object or physical article, the new features of that physical article can be highlighted by explaining what the physical differences are between your invention and anything else available and then claiming those differences.
The other way of satisfying the novelty requirement is to show that what you have invented is a new combination of existing objects and explain to the Patent Office, that yes, the things that I am using to make this new thing all exist, but I have put them in a new combination to make something brand new. In this case, the pieces were all there but they were not put together until your invention came along. If your invention puts those pieces together in an unobvious and new way, it may meet the novelty requirement. Here, the test really is if the existing things can be grouped together to solve something new. The combination of things that were pre-existing, when put together should not just be a collection of parts. As a whole, your invention should incorporate the preexisting parts such that they function together to perform a certain task. That useful function should be new.
The third way to satisfy the novelty requirement is to show that your invention creates a new use for an existing object. You might have a physical product but now it was used to do something. Now you have discovered this physical product that was used to basically kill weeds can now be used to grow a new kind of flower. That new use for an existing product can also be potentially protected through patents that satisfy the novelty requirement.
By way of summary, you can satisfy the novelty requirement by showing the physical features of what is new. You can also satisfy it by demonstrating that your invention is a new combination of existing things. The third way to satisfy the novelty requirement is to show that there is a new use for an existing product or service.