Bits target, Increase/Decrease in ease of mine
Decreasing the target makes finding the correct block hash harder because the range of possible values is smaller. There are less numbers for 1 to 10 than there are from 1 to 100. So by making the target smaller, it becomes less likely for the correct hash to be found and thus the difficulty increases.

Increasing the target makes finding the correct block hash easier because the range of possible values is greater. By making the target larger, it becomes more likely for the correct hash to be found and thus the difficulty decreases.

The relationship between difficulty and the target is inverse.