Distilling is really just the act of separating two liquids that have been mixed together. The alcohol itself in alcoholic beverages is made by yeast eating sugars in a process of fermentation. This is how we make bear and wine and mead.

However this fermented liquid will contain a relatively low amount of alcohol. If we want something stronger we need to separate the alcohol from the rest of the liquid, and this is where distillation comes in.

So if we're using bananas as a source we could start by fermenting banana juice, creating an alcoholic banana wine. If we wanted to make it more potent, a higher percentage of alcohol, we could then distill our banana wine and end up with banana brandy.