Small packet, also called packages, is a postal term that is internationally defined as
mail
The mail or post is a system for physically transporting postcards, letter (message), letters, and parcel (package), parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid ...
s less than 2 kg.
Commonly, small items that are not flat enough to be sent as ordinary letter would be sent as small packets.
Gallery
File:Missing CN22 declaration.jpg, Small packets sent from Ukraine
File:UK Royal Mail small packet to New York, USA.jpg, Small packets sent from the UK
File:Japan air mail small packet to the UK.jpg, A Japan mail labeled as "small packets"
References
{{Authority control
Postal systems
Philatelic terminology