Key datastructure is a data statucture or container which keeps key value pair. For a search the key is passed to check that the key is present in DS or not.

If the reflection is over the x value, the x-value does not change.

The x value is the first of a coordinate pair and tells you how far from the y axis the point is.

An ordered pair has two values. You need to define the absolute value of an ordered pair before the question can be answered. There are many possible metrics.

for example in a Database:

The key is CITY and the value is Los Angels