What is seed in RAND function in SQL Server I am not able to understand as to what is the use of seed in the RAND function of SQL Server?

I read the below link but i am not able to understand what it is doing?
Link 1
Link 2
Link 3

After trying out few random seed number i found the below results:-

Select RAND(1) - 0.713591993212924
Select RAND(2) - 0.713610626184182
Select RAND(3) - 0.71362925915544
Select RAND(4) - 0.713647892126698
Select RAND(5) - 0.713666525097956


Whenever i provide the seed from 1 to 5 i always get the number that i have mentioned above.

Why is that so?
Microsoft docs explains this in details here: apparently RAND() returns a really random result only if it is called without specifying a seed value (because in this case seed itself is assigned randonly).

So calling RAND() without seed should always return a different value, while calling RAND(seed) should always return the same result if called with the same seed.

Here is an excerpt from Microsoft docs:


  Arguments seed Is an integer expression (tinyint, smallint, or int)
  that gives the seed value. If seed is not specified, the SQL Server
  Database Engine assigns a seed value at random. For a specified seed
  value, the result returned is always the same.
  
  Remarks 
  Repetitive calls of RAND() with the same seed value return the
  same results.