child tables for a give parent table

What does this RDBMS jargon mean
"Child Tables for a given parent table". Can any body explain this in plain english to me?

child table are those tables that references a parent table

for example table emp and table dept

dept would be the parent table and emp the child

emp would have a foreign key that references dept primary key

the values in foreign key column in emp must be null (depends on how´s ur relationship) or one of PK in dept

does this help...?

thanks Pando. The explanation is perfect.

When a relationship is made between entities, there are 3 types; 1 Identifying 2 Non-identifying 3 Non-Specific.

The 2nd major category is "existence". There are 2; one is "mandatory" and the other is "Optional".

When you say Identifying and Mandatory then the attribute will become part of the primary key in the child table, otherwise it will not become part of PK.