Understanding Your Fertility Window: A Clear Explanation

Question
Figuring out my fertility window involves math, so I'm confused.
When I look at online ovulation calendars, (babyhopes.com is the one I'm thinking of) they say you are most fertile 2 days prior to ovulation.  But I thought I would be also fertile the day of ovulation and two days after?  I don't have a clear picture in my mind of where the egg needs to be when it is fertilized.  Can it be headed down the fallopian tube?

Answer
Hi HPC,
You are fertile in the interim betwen periods; in essence 2 weeks out of four. You need to take basal temperatures in the AM prior to getting out of bed. When the basal temp rises, you are at peak. The egg is fertilized in the tube and then descends to the uterus where it takes hold to start the pregnancy.