Referring to the post under General Question

Does anyone know how to use offset for specific value? such as
Under column A, there is a list of value.
Under column B, there is a list of value.
In cell C1, I input any value listed under the column A, for example "xxx"
is found under cell A6,
In cell D1, return the value "yyy", which is found under cell B6.

Does anyone have any suggestion?
Thank you in advance
Eric Choi