The word counter has several related meanings:

1. A flat surface in a kitchen or store where work gets done. The kitchen counter is where you might roll out cookie dough or where your parents prepare dinner. At a store, you place items on the counter to pay for them, and the clerk stands behind it to help customers.
2. To respond to an argument or action by opposing it. When your friend argues that cats make better pets than dogs, you might counter by pointing out that dogs are more loyal companions. In a debate, each side tries to counter the other's points. A boxer might counter an opponent's punch by blocking it and immediately striking back.
3. Something that counts or keeps track. You might use a counter to track how many customers enter a store, or how many jumping jacks you've completed.

When something runs counter to your plans, it works against what you hoped would happen.