What is hot raspberry puree? I have a caramel recipe that calls for hot raspberry puree to be added near the end of cooking. I'm assuming that the seeds are supposed to be removed, so how is this different from raspberry juice?

I have a bag of frozen raspberries. Could I just thaw them and put them through a mesh sieve (the way I would make juice)?
Raspberries aren't just seeds and juice, though they're certainly not as fleshy as some fruits. The difference between apple puree (apple sauce) and apple juice is much more obvious. In any case, you should be fine forcing them through a sieve as you suggest.