I understood the difference between the offers and the products, but how to know if it is necessary to send my products?
1. Either you have the certainty that your products do not exist on AliExpress, i.e. they are not known through their EAN code, in this case you will need to create your products in order to be able to publish offers on them.
2. You resell known manufactured products whose EAN code is known in AliExpress, so you are sure that your products exist on AliExpress, so follow the tutorial products creation.
3. If you have any doubt, you sell such products marketed by one or more suppliers that could be sold on AliExpress. In this case your products may already exist on AliExpress and then you could send your offers without waiting integration.
In this case follow the initial offers publishing tutorial.
Then, if there are any products to create, you can create a posteriori, AliExpress will then create the products that do not exist in their catalog, you will follow the products creation tutorial.