This Article lists the Reserved Keywords in SQL Server. The identifiers we give to the database objects like column names and table names etc should not use these words. If you want to use them, then you should always use the Delimited format by enclosing them in square brackets  or double quotation marks (“”)
SQL Server Identifiers
Identifiers are the name we give to the Servers, Databases, and Database objects, such as Tables, Views, Columns, Indexes, Triggers, Procedures, Constraints, and Rules, etc. They must uniquely identify them. We then use the identifier to refer to the server, database, table whenever we want to use them. There are certain rules & restrictions that we must follow when we choose the name for the identifier.