Kartris will do a fairly good job of filling meta-tags and page title for pages automatically. For example, on a product page, it will use the product name in the title tag, and fill the description with a truncated section of text from the product description. The keywords will generally use the ContentText_DefaultMetaKeywords value.
But you can override these default values in many cases.
For example, when creating or editing a product, category, knowledgebase article or custom page, you can open extra fields with the [+]SEO link. This allows you to override the default values that Kartris will insert, and specify the exact text you want to appear.
This can be useful if you want to keep the product or category name short and concise, but have the page title itself longer and with more keywords to help improve page indexing.
You don't need to duplicate your product names and descriptions in these SEO fields. Only use these fields if you want those meta tags to be different to the actual product name and description.
