Your classes will likely have data members so how do you work with these data members? Should they be public? Private? Do you let other code access them directly? And what’s the difference between a field and a property? This episode will help you get and set your data members.
I recommend that you keep your data members private and to create getter and setter methods if you’re using C++ and to create properties if you’re using C#. Even if you don’t think you’ll need the methods or properties right away, they give you so much more control over how your class is used and almost all classes will eventually want this control. There’s just too many ways that outside code can misuse direct access to your class data.
And if that’s not enough of a reason, then consider the benefits of testing. Methods and properties help to reduce the exposed surface area of your class and provide well known entry points which can be better tested. Any problem found can then be fixed in one place instead of then trying to figure out where are all the other places in your code where you were working directly with the data.