What a sweet name!
Since leading zeros of a binary number can be dropped,
it is safe to not actually include the first 1.
There will always be one, so there is no need to show it.
The exponent is adusted so that the most significant 1 is
in the one's place of the mantissa.
For example: say that you wish to represent
00011.00101101
as a float.
11.00101101
1.100101101 × 21
100101101 × 21
10010110100000000000000 × 21
10010110100000000000000