I appreciate you reaching out here in the Community, @suzannek1. Let me provide you with information about the differences between Category details and Item details. 

Category details refers to the accounts listed in your chart of accounts. It allows you to select an equity, expense, asset, and more to post the charge directly to that account. Examples are recording for advertising and marketing fees, bad debt, contract labor, and more.

Item details refers to the specific products and services you purchase from a vendor or sell to your customer. It is also linked to an account in the chart of accounts, and each product/service has an income or expense account.

The choice between category details and item details in creating a check in QuickBooks Online (QBO) depends on the nature of the expense and the level of detail required for accurate financial tracking.

As you record your transactions, you may also consider tagging transactions to get more insights into your sales and expenses.

Please don't hesitate to reply to this post if you have further questions about category and item details in creating transactions. I'd be glad to help you anytime. Have a great day.