Dimensions

I am not clear and would be thankful if someone could explain the following

1. A dimension in a cube consists of 1 DIMID and 10 characteristic (SIDs)

2. The number of records in this dimension is about 900,000 records - this means that there are about 900,000 DIMID created is that correct?

3. The DIMID is a generated number and is not equal to the most granular characteristic in the dimension, is that correct?

Thanks