A CAST That Appears To Use A Template. Is This Correct?

I need some feedback on how this sql is perfroming a cast. I have used CAST before, but I am
looking at a stored procedure, and the CAST looks slightly different. Usually when I do a
cast, it is of the form CAST(ColumnName,DataType) but this cast is slightly different as they
appear to be using some type of template to cast with. Here is the code. I will put line numbers in for reference.

 

1    CREATE TABLE #Groups
2    (PartyId uniqueidentifier)
3    INSERT INTO #Groups (PartyId)
4    SELECT PartyId
5    FROM ttg_sfGroupsByPartyId(@PartyId)
6
7    IF (@PortalId = CAST('00000000-0000-0000-0000-000000000000' AS uniqueidentifier) AND8
8 @TabId = CAST('00000000-0000-0000-0000-000000000000' AS uniqueidentifier))
0     BEGIN

Also just to let you know, the the values PartyId, and PortalId are GUIDS.

So, I guess my question is, are they using a kind of template to format the data? So look at lines
7 and 8. Are they using some type of template to signal the compiler, that the data will be of that
format and will be seperated by dash symbols?