Hello.
It is possible to create products variations in 2 ways: simple products with custom options (do not allow to track stock os sold items, but are easy to create) and configurable products (allows to create 1 parent configurable products and link to it simple products - but is might be difficult).
Let me explain in more details and offer links for further reference.
Simple Products with Custom Options - how to create them
You create product os simple type - like T-Shirt and in tab 'Custom options' add select option of drop-down input type and add values like - s, m, l, xl etc
Here is what you get -
Configurable product with associated simple products - how to create
First of all you need to go to Catalog ->L Attributes -> Manage attributes and add new attribute Size in attribute set that you will use for product creation. Note it is required to be:
- drop-down,
- scope- global
- should be assigned to configurable and simple products
After that you need to create configurable product and in tab Associated Products create all size variations (they will be created as simple products of different sizes) or if the goods are ready-made link them to parent configurable -
Here is also an article with details explanation on configurable products creation -
https://www.mag-manager.com/useful-articles/tipstricks/what-is-magento-configurable-product-how-to-c...
Update: Just noticed that you are in section for Magento 2, there things with configurable are easier, as you can use 'Create Configurations' option -
