Bridge table is also known as helper table or reference table. If there is a many to many relationship between fact table and dimension table then we use bridge table to resolve this relationship (this bridge table is anology to associative entity between two entities having many to many relation ships). Bridge table is also used to flatten out the hierarchy in the dimension table.
In database management systems following the relational model,a junction table sometimes known as cross reference table,bridge table,map table,join table and link table,is a table having common fields from 2 tables.It is on the many side of a one-to-many relationship with the other 2 tables. junctions tables are employed when dealing with many-to-many relationships in a database.