What is the difference between orders and invoices?

[Chris K. \(Ski\) <kac...@at...>]

I am setting up SQL Ledger for the first time and playing around with it.
I both sell a service and sell parts.  From playing with SQL Ledger it seems
that:

- orders can be converted into invoices and vice versa

- I cannot post payments to an order

cheers,

ski