Check out example codes for "return columns from table sql". It will help you in understanding the concepts better.

Code Example 1

SELECT *
FROM INFORMATION_SCHEMA.COLUMNS -- INFORMATION_SCHEMA is an ANSI-standard (American National Standard Institute) set of read-only views which provide information about all of the tables, views, columns, and procedures in a database
WHERE TABLE_NAME = N'Customers' -- "N" defines the subsequent string (the string after the N) as being in unicode

Code Example 2

SELECT *
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_NAME = N'Customers' 
-- INFORMATION_SCHEMA is an ANSI-standard (American National Standard Institute) set of read-only views which provide information about all of the tables, views, columns, and procedures in a database
-- "N" defines the subsequent string (the string after the N) as being in unicode

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