I understand the difference -- I have read a lot and still come away a bit mystified.
I have an arduino based project (technically ATTiny85) The arduino can run off "house power", but when that power is cut off; I need to to run from batteries.
There are two ways to charge them -- one a small solar cell which should be matched for a bit more than the load of the arduino; so it should make up for night time w/o solar. The 2nd way is to plug a pc into to download data.
From reading, I get mixed info on the "proper" way to do it. I plug into the arduino to get the info; that provides power to the power charger, which powers the batteries, ditto for the solar. But some have hinted "there's more to it" than just hooking it up in parallel.
Would someone give some guidance?