Wikibase/Schema/wb terms

term_row_id

 * Unique row ID.

term_entity_type
Contains a plain text string with one of the following values:
 * — means  refers to an item
 * — it refers to a property

term_language

 * examples: "ab", "ace", "aeb", "aeb-arab", "aeb-latn", "be-x-old", "de", "de-at", "de-ch", "de-formal", "en", "en-ca", "en-gb"
 * A complete list can be found [where?]

term_type
Contains a plain text string with one of the following values:
 * — the main label to be used for representing the described Entity in Wikidata in the specific languages, e.g., Georgia could be an English label. For properties, the label may be referred as the "name", as it is unique for the particular language (according to the Wikibase DataModel).
 * — a brief description to clarify the meaning of the label (which may be ambiguous), e.g., a country in the Caucasus could be an English description. The intended use is mainly disambiguation when displaying multiple entities with the same label, for selection. For items (as opposed to properties), the combination of label and description is unique for one particular language, if both label and description are defined (according to the Wikibase DataModel).
 * — Also known as — alternative label in the selected languages, used mainly for searching for items by their name. There may be multiple alias entries per entry_id per language.

More details: Wikibase/DataModel § EntityDescriptions of Items and Properties

term_search_key

 * The same value as  contains, but normalized for search, e.g. all lowercase

Versions
Current as of Wikibase 0.4 (19 Feb 2013) +--+--+--+-+-++ +--+--+--+-+-++ +--+--+--+-+-++
 * Field           | Type             | Null | Key | Default | Extra          |
 * term_row_id     | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
 * term_entity_id  | int(10) unsigned | NO   | MUL | NULL    |                |
 * term_entity_type | varbinary(32)   | NO   | MUL | NULL    |                |
 * term_language   | varbinary(32)    | NO   | MUL | NULL    |                |
 * term_type       | varbinary(32)    | NO   | MUL | NULL    |                |
 * term_text       | varbinary(255)   | NO   | MUL | NULL    |                |
 * term_search_key | varbinary(255)   | NO   | MUL | NULL    |                |

Restrictions
According to the Wikibase DataModel,