SMS = "Text" (up to 160 characters of plaintext ASCII, longer messages are segmented)
MMS = "Picture Messaging" (SMS with file attachment)
MMS protocol allows any sort of file or files to be attached. But in practice, the software built into most phones will only really work with common photo formats, sometimes also common audio formats. Other (better) softwares can always be installed, but many people don't bother.
All current Public Mobile plans have "Unlimited International Text" with "Unlimited International Picture Messaging". You could send or receive as many texts as you like (with or without attached images) to or from anywhere in the world for free as long as your phone is in Canada with an active plan (or is in USA with an active US Roaming add-on).
MMS requires active cellular data. And Public Mobile's APN settings.
Each MMS is logged in Self-Serve usage history as an "MMS Event" which consumes 0.00MB of your data provision. (This data usage is essentially paid for by Public Mobile, not by the subscriber.)
If data isn't active then you'll just see a "click to retry/upload/download" placeholder instead of a picture. The network usually stores undelivered messages/attachments for a while.
Some people have reported difficulties with Texting to/from phones in countries which aren't part of Public Mobile's "International" list. It doesn't seem to be a problem for most people.
Some legacy plans had a variety of different (but typically more limited) Text provisions and conditions. But legacy plans aren't available for new number ports or activations.
