Q:

What does master..sysdatabases and test..sysobjects mean?

I am learning how to use SQL server recently. I do not understand why use master..sysdatabases and test..sysobjects in the following statements:
select name from [master]..[sysdatabases] where dbid=1;
select count(1) from [test]..[sysobjects] where xtype = 'U';

What does the 1 in count(1) mean? Does it mean the first column?
Thanks for any helpful answers.

A:

Your first line basically gets the name of the master database (it looks at the list of all databases, and returns the name of the database with the ID of 1, which in this case is generally going to be 'master').
Do a  to see all the databases on a server:
SELECT * FROM [master]..[sysdatabases]

Note that the row with "dbid" = 1, is the row for the "master" database, which is a system database present on all SQL Server instances.
Your second line counts the number of rows in the sysobjects collection in the database named 'test' where the type is a user table (i.e. not a stored procedure, not a system table, etc).
In the expression "[x]..[y]", the 'x' is the name of the database, and 'y' is the name of the table or view within that database.
If you had a database named "Foo", and in there was a table named "Bar", then this statement would return the count of rows in that table:
SELECT COUNT(1) FROM [Foo]..[Bar]

As Ed Gibbs above described, the '1' is just a place-holder for counting the total number of rows in the most efficient way possible on any possible database or version.  It's become a sort of short-hand way of counting.

