Traditional inverters gather power from all or most of the panels in an installation and use transformers, capacitors and switches to change it from directcurrenttoalternatingcurrent.
One of the considerations was the relative safety of directcurrent - the first electric chair seems to have been built (and then used) to prove that alternatingcurrent was more of a killer.
Their job is to convert high-voltage alternatingcurrent from the mains into low-voltage directcurrent for mobile phones, laptops, iPods and other electronic gadgets.