Ancestry.Com is a useful tool in aiding people in genealogy research because of the large number of original source records they have. Now you have to distinguish between the records they have obtained and put online and their subscriber submitted family trees. Information in family trees on ANY website must be viewed cautiously. They are not submitted by some experts working for the websites but by folks like you and me, the subscribers. Even when you see the absolute same information on the same people from many different subscribers that doesn't mean the information is accurate. Too many people copy without verifying. So the ads Ancestry.Com has, many are right on but when the person in the ads gets their info from submitted family trees if they don't verify the information with documents and records, they are damfules. Actually if you find any of your family in an online family tree and there is wrong information, those that run the websites will tell you that is between you and the other subscriber. There is no way they can hire people to check all the information people submit. It would be too costly.
Ancestry.Com has
a) all the U.S. censuses through 1930. The 1940 and later are not available to the public yet.
b) vital records(birth,marriage and death) from many U.S. states
c) immigration records. I have a friend whose mother came from Calbria and father from Sicily. She has made many trips to the National Archives in Washington. She says now Ancestry.Com has all the records on her family that the National Archives has.
d)some land, wills and other records
e) military draft and enlistment records.
f) many old newspapers online.
When I go into their website and I go under "search" then on the next page, I click on "Old Search " which is on the right toward the top as I feel it is far more functional than their New Search which is just prettier.
Don't expect to find information on the living on any website as that can be an invasion of privacy and can lead to identity theft. If you find Ancestry.Com too pricey, your public library might have a subscription to it you can use for free. You might want to test the waters on it at your public library first.
Now a good free website you can use along with Ancestry.Com that has lots of records it the one FamilySearch.org has where they are putting records that the Latter Day Saints(Mormon) Church online.
They have records on people all over the world, not just Mormons.
https://www.familysearch.org/
If you haven't you should check a Family History Center at a Mormon Church. They can order microfilm for you to view for a fee of about $3. I have never had them to try and convert me nor have heard of them doing that to anyone else that has used their resources
Even if your grandparents are elderly and not as sharp as they use to be sometimes they will remember things of the past when they won't remember if they have taken their medicine. It would be wise to tape them if they will let you. They might get into telling stories of days gone by you wouldn't write down but in those stories if you go back and listen to the tape again after doing research you might hear clues you didn't hear the first time around.