What do you mean by slow dimensions?

Slowly changing dimension means these dimensions will change according to time,
Ex: In Bank- a/c number, A/c name , address is there then if v change address then address will be a slowly changing dimension for that,
It is of 3 types
Type-I
Type-II
Type-III.

SCD means it explainsexactly how the changed data has been loaded into the target database.
There are three types of SCD
SCD1
SCD2
SCD3

SCD1: It holds only current data.
SCD2: It holds the current+historical data.for every datachange it inserts a new record.
SCD3: It holds the current and immediate previous data.