If you’ve got a few solar panels lying around, or even if you want some 120/230 V AC power from a few 12 Volt batteries, you’ll need a power inverter. Sure, you can drop on down to any big box store ...
According to textbooks, a sine wave is a wave whose form resembles a sine curve. Often in power electronics, we need a sine wave generator for some applications; a dc/ac power inverter, for example.