Category Creation in magento
Whenever you created category in magento then the created category info will be insert into following tables in magento
1. catalog_category_entity
2. catalog_category_entity_datetime
3. catalog_category_entity_decimal
4. catalog_category_entity_int
5. catalog_category_entity_text
6. catalog_category_entity_varchar
7. catalog_category_flat

remember if you want import category in magento so you simply these these table data export from another database and import whenever you want that its .