Value Table

This is maintained at Domain Level.

When ever you create a domain , you can entered allowed
values.   For example  you go to Domain   SHKZG -
Debit/credit indicator.  Here only allowed values is H or S.

When ever you use this Domain, the system will forces you to
enter only these values.

This is a sort of master check . To be maintained as a
customization object. This mean that if you want to enter
values to this table you have to create a development
request & transport the same.

Check table

For example you have Employee master table & Employee
Transaction table.

When ever an employee Transacts we need to check whether
that employee exists , so we can refer to the employee
master table.

This is nothing but a Parent & Child relationship .  Here
data can be maintained at client level , no development
involved.

As per DBMS what we call foregin key table, is called as
check table in SAP.

There is 1 more important Difference in Value Table and
Check Table is that:
 
1. The contents of the check will be used as an input
help(F4 Help) for a particular field on which a check table
is assigned.
    But the contents of Value Table are never used in Input
Help.
 
The Heirarchy which decides from where to used the Input
Help is:
1. Input help defined explicitly in ABAP Program or Dialog
Module.
2. Input Help Attached to the referenced Database Table field.
3. Using the contents of Check Table as an input help if
neither (1) or (2) help are there.
4. Input help from Fixed value or Value range given in Domain.