Stupid Question: What does the duration in seconds mean on things that are for puring healing? For example:

Prickly Pear Fruit: HP +3 (10s)

After 10 seconds, I see the effect has worn off but the recovered hit points still exist. What does the duration mean? I'm not playing in hard core mode.

It means that you recover 3 HP per second for ten seconds. So when it wears off, you will have recovered 30 total HP, up to your max.

It heals at +3 HP per second for 10 seconds.

Thanks, that makes sense.