Products (API Name : Product2) is the Standard salesforce Object.These include all the Products in Salesforce.Now when you add these Products into an Opportunity , they are then called OpportunityLineItems.These OpportunityLineItems are the Opportunity Products.
Products are a catalog of products/items that you company can sell. No pricing information (by default) is included, just description, category, code, etc.
Opportunity Products are line items on an opportunity. It will include pricing information for that particular order. It’s like a itemization of products that are included with your opportunity.