When given AGE APPROPRIATE GAMES and monitored by the parents when playing online with others (which honestly shouldn't be allowed until the teen years) the effects are actually quite nice.
Increased hand-eye coordination, better reading skills, better language comprehension, and puzzle solving skills are among some of the really nice things that a child can learn when exposed to video games. It can also potentially increase their imagination depending on what games they are playing.
If you're letting your child play games keep the rating in mind. In the US at least the ratings are E, E 10+, T, M and AO which are pretty self-explanatory as everyone, everyone 10 and up, teen (13+), mature (18+) and adults only (21+) respectively. Most physical stores such as a Game Stop are not allowed to carry AO rated games and cannot sell M rated games to anyone under the age of 18 for legal reasons.
Chances are a question like this is asked out of concern for a child having video games. But so long as a parent or other responsible adult keeps the rating in mind and looks at why a game has a certain rating they can judge if a child has the maturity to handle a game.
The sad reality, however, is that many parents treat video games as a way to keep it so they don't have to deal with their children. So they buy a popular game like Call of Duty or PUBG/Fortnite for their 8 year old because all their friends are playing and they want in and don't pay attention to the rating or the fact that it's online play with anyone who has the game and not just their friends and the kids are left unattended in a playground full of dangers they are not equipped to navigate. Then said parents refuse to take blame when their kids learn things or are exposed to things they shouldn't be because the parent wasn't watching them when they do not know any better and are learning from other sources. But when parents step up and make sure what game their child is playing is age and content appropriate video games are quite nice :)