The interaction problem is a supposed problem for Dualism, the view of the mind that humans have two parts, an immaterial mind and the body
I will state it as it follows:
1-The mind and body are two separate substances, and have no shared properties
2-two substances need one shared property to interact
3-the mind and body cannot interact
However, the mind and body do clearly act. Whether you are a materialistic, Idealist or whatever, you most likely belief that your thoughts cause your actions. You need to drop either one or two.
Two can be supported by the fact it has wide confirmation: a hammer and a nail have the property of being physical, and ideas that interact with each other have the property of being ideas.