An associate company is like having a really good friend that you do a lot of things with. You both have your own things going on, but you also work together on some things.
For example, let's say you and your friend start a lemonade stand together. You both put in some money to buy the ingredients and make the lemonade. You also both decide how much to charge for the lemonade and how to split the money you make.
In this case, your friend is your associate company because you are working together to make money. You both have some control over the lemonade stand, but you don't own it completely by yourself.
The same thing can happen with bigger companies. Sometimes one big company will work closely with another smaller company. They might invest some money in the smaller company or work together on a project. In this case, the bigger company is like your friend who has more money and resources to help the smaller company.
So basically, an associate company is when two or more companies work together on something, but they each still have their own separate businesses too.