If more than one table is named in the FROM clause, they are all implicitly joined. This means that every possible combination of rows (one from each table) is derived. In addition, this concatenation is the table on which the rest of the query operates. The concatenated table is called a Cartesian product or cross join. Typically, you want to eliminate most of the rows and focus on the data you want. To do this, use the WHERE clause.

The standard join is also referred to as an inner join and is simply the regular SQL WHERE clause, for example:
WHERE [table1.]column1 = [constant | [table2.]column2]