UID = Unique Identifier
Many collections of data (like Customers, Sales and Purchase Orders, Picking Notes, Deliveries etc need to be uniquely identified. The ID can be just numbers, just letters or a combination of both (depending on what is being identified. The UID part is often preceded by a letter to make it more obvious which ID it is.
For example
Customer Code: CUS001 - You can have the same Customer Code over multiple sites but it can only occur once per site - once set it is not possible to change this Code.
OUID or Order UID = Sales Order Identifier - a sequential series of numbers generated by the system. This number will be used only once throughout the whole system.
PAID OR Pre-Advice ID = Pre-Advice Identifier - a sequential series of numbers generated by the system. This number will be used only once throughout the whole system.
PUID Or Pick ID = Pick Note ID - a sequential series of numbers generated by the system. This number will be used only once throughout the whole system. Please note, if you unpick and then repick a Sales Order the original PUID will be discarded and a new one generated for the new Pick. Whilst the OUID and PAID will always find there associated Orders, the PUID will no longer be valid once the Orders have been unpicked.