The word is pronounced as /ˈəʊvərɔːl/ in British English and /ˈoʊvərɔːl/ in American English. You say it in three parts: first "o-ver," like saying "over" but quickly, and then "all," just like the word that means everything or completely.
"Overall" means considering everything or in general. When you talk about the overall situation, you're looking at the big picture, not just one part of it. It can also describe a type of clothing that covers most of the body, like what some people wear for work to protect their clothes underneath, but this use is less common when talking about general topics.
The word "overall" comes from the Middle English period, combining "over," which means "above" or "covering," with "all," meaning the whole of something. It started being used around the 13th to 14th centuries. Originally, it described something that covers everything or is about the whole of something when considering all its parts. Over time, its use expanded to not just describe things that cover but also ideas or situations that include everything involved.