Homogeneous substances or mixtures are always considered to be pure substances or mixtures. They can be explained as mixtures that have a single phase. That means when you mix them together; they are evenly mixed, that you cannot identify the difference between them, and you can also not separate them physically.
For example, the mixture of kerosene and petrol is a homogeneous mixture; you won't physically see the difference between them. On the other hand, heterogeneous substances or mixtures are considered to be impure substances. They do not have a single phase. This simply means that heterogeneous mixtures are not evenly mixed together.
When you separate them, you can still physically see the difference or separate the mixture. They will form two different layers. For example, the mixture of water and oil can be physically seen to form different layers. So, we can explain homogeneous to be a single thing, while heterogeneous can be described as more than one thing.