Anti-intellectualism is when people don't value education and learning new things. It's like if you had a toy and someone said "reading books or going to school is boring, just play with your toy instead!" This means they don't think it's important to learn new things or understand the world around them.
But just like how it's important to eat healthy to grow up strong, it's important to learn new things to grow up smart. When we learn about science and history and math, we can understand things better and make good decisions. So being anti-intellectual is not good because it means people might make bad choices because they don't understand things very well.