What is the difference between a union and a inner join? _access

The Inner join is where the two tables do the same part of the record to produce a recordset,
Union is the resulting two recordset (field to be the same) and together to become a new recordset

Select a.field1,b.field2 from Table1 A inner join Table2 B on A.field2=b.field2 where ....
Select Field1 from Table1 Union select Field2 from Table2
Programme II,

Select A.id,a.title,b.content from table 1 as a, table 2 as B where a.id=b.id order by a.id

RS ("id")
RS ("title")
RS ("content")

Other:
Create a new table xxx

sql= "INSERT into XXX select P.id,p.title,m.content in" inner join Miaoshu M on P.id=m.id "
Conn.execute SQL