I am working in USA with H1B visa. I have a question about renewals.
What is the difference between visarenewal and Status renewal? How it impacts visa holder?
A U.S. visa is a document whose sole purpose is for entering the United States. The visa expiration date is the last day the you can use the visa to enter. You can only get or renew a visa at a U.S. consulate outside the U.S.; this is because you need to first be "outside" the U.S. in order to enter the U.S.
The status is what allows you to stay in the U.S. When you enter the U.S., you will get an I-94 (recently, I-94s have been automated, so you won't get a paper copy anymore; you can print it out from the website if you really need it), which contains a date until which you are allowed to stay in the U.S. For some statuses, like F-1 and J-1, additional documents, like I-20 (for F) and DS-2019 (for J) are also used to determine the duration of status.
You don't need a valid visa to stay in the U.S. (it can be expired for years), as long as you have a valid status. Conversely, you cannot stay in the U.S. if your status has expired (and you're not currently extending or changing it), even if you have a valid visa.
Before your status expires, you can apply to change or extend your status in the U.S. If it is approved, you will get a new I-94 signifying a new date when your status expires. Note that this has nothing to do with the visa; if you need to leave the U.S. and come back, you still need to get a visa at a U.S. consulate if you no longer have a valid visa.