Is there a difference between an IMO and an IPMO

Is there a difference between international money orders and international POSTAL money orders?

I get money orders at a place and it says "International" on it, so... I don't know...

Some people claim to be able to process only IPMO's at their banks. Why, I don't know. That's why some sellers ask for them. IPMO's cost more as well. For me, it's either $.75 or $1.25 for an IMO from my credit union, where IPMO's are around $3.50.