Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me.
Now the psalm turns to a darker note – this part of the psalm is why it's so often read at funerals (and yet not at Thanksgiving, perhaps?).
Even though the speaker walks in the shadow of death, he doesn't have any fear because God is there.
God's shepherd's rod and staff comfort the speaker. These two things are actually the same thing – a big stick that a shepherd uses to guide the flock.
Images of staffs are common in both the Hebrew Bible and the New Testament. You might remember that Moses had a staff that he used to part the waters of the Red Sea. Also, one of the symbols for the Catholic pope is a staff.
What is this valley anyway? Is its name "Shadow of Death Valley"? Isn't that somewhere in California? Where do I find it on a map?
All kidding aside, a valley is a place surrounded by hills or mountains, which often cast a shadow below. So this is not some pleasant little valley, and those imposing mountains that surround it are symbolic of death. It's a place of danger where many bad things or "evils" could occur.
Some people think that the valley is also a symbol of general despair or dark times, as opposed to a specific fear of death.
But the speaker has absolute trust that even in a dangerous environment the shepherd will guide him in the right way.
You might interpret that the path through the valley is the "path of righteousness."
The "yea" at the beginning of the line isn't celebratory – "Valley of Death! Yesss!" In the New Revised Standard Version translation of the Bible, the "yea, though" is translated to "even though."