I have two models in my application builder, one for Customers and one for Products, i want to know if i can make both communicate or make links between two entities which are in 2 different models ?

It is not possible to make references from an entity in one model to another entity in a different model.

If your business requirement is for a Customer to buy a Product or a Product to be owned by a Customer then you should have these entities in the same model, and potentially have different Applications for Customer and Product.

If you have to keep Customer and Product in different models, you can add a Product entity to your Customer model (or the opposite) and implement a data synchronization flow between both data locations so that Products authored in your Product instance automatically flow to your Customer data location.