IQueryable

If Someone could help me understand this piece of code bellow

public<Product> GetProducts([QueryString("id")] int? categoryId)
        {
            var _db = new WingtipToys.Models.ProductContext();
                IQueryable<Product> query = _db.Products;
                if (categoryId.HasValue && categoryId > 0)
                {
                    query = query.Where(p => p.CategoryID == categoryId);
                }
                return query;
        }

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yguyon28Asked:
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käµfm³d 👽Commented:
You have a method named GetProducts, which takes in a (nullable) integer. This value comes from the querystring parameter named "id", which would be passed in a web request to your service/web page. Inside the method, you create a new database context which you will use to interact with your database. From the database, you will be retrieving information from the Products table. In your code, the Products table is represented as  an IQueryable of Product--vaguely like a list of products. An IQueryable just means that this is something that you can query with LINQ, and typically the data originates from a database. So you search through this list of products using the categoryId value that came in as a parameter. Wherever the category ID matches in a database record (from the IQueryable), you will return it from the method.
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