Definitely in the database: that's were data are supposed to go.

But you do not need to make a separate table for it (as castaway already suggested). Still if ever you want to change the level descriptions, you will need to adjust the descriptions everywhere in the database, UNLESS you code these descriptions as an ENUM data field which will allow you up to 255 different members in the ENUM in one byte or 65535 different members in two bytes.

Changing the level descriptions is then as simple as changing the definition of the ENUM field.