The Object_ID() takes in the object name and object type as parameters. The object name is the object used and the object type is the type of object used in a schema.
For example to check if a table exists in a database, use this query :
IF OBJECT_ID ('AdventureWorks.dbo.AWBuildVersion','U') IS NOT NULL
Print 'Table Exists'
Print 'Table Does Not Exists'
where 'AdventureWorks.dbo.AWBuildVersion' is the object name and 'U' is the object type which represents a table
Similarly you can check for a stored procedure or a view by specifying the correct object type. You can get an entire list of object types over here.
To check if a database exists, you can use the DB_ID() function as shown below :
IF db_id('AdventureWorks') IS NOT NULL
Print 'Database Exists'
Print 'Database Does Not Exists'