1) You are on the right track in wanting to know if these are good or bad websites. Since you are new to the game, and since I, and possibly you, do not know PC Doctor, there is no particular reason to trust that program to decide what sites we visit and do not visit. On the other hand, if you can determine that the program has a long history and good reputation, and uses open and well defined methods of determining what sites are blocked and how that is done, then the Dr. may be OK
For my purposes I do my site blocking using the "hosts" file, which is a natural, preexisting Windows feature. More below ->
2) Blocking web sites should not disable a software program on your machine. It might make some online programs (software such as online tax preparation, etc.) which are not on your machine but on the internet, if access to the sites hosting those programs are blocked.
3) The numbers you are seeing are the addresses used on the internet to find locations on the internet - they are WWW street addresses. All the "www.xyz.com" addresses you see are "domain names". Each domain name is associated with a computer facility which hosts the information or services provided by the people who own or control the domain. Those computer facilities have specific computer friendly addresses, under the IP or Internet Protocol. Your computer also has a specific address, assigned by your ISP or information service provider. These are called IP addresses, and that is what is showing up on your screen.
These addresses allow a computer based communications network - the internet or www - to pass messages back and forth between your computer and the computer hosting the information or services offered by the domain.
The translation between the human friendly domain name
www.xyz.com and the machine friendly IP address is handled by specialized computers, using tables listing the relationship between every domain name and the IP address numbers associated with each of them. This function is called DNS, if you run accross it.
You can tell what these numbers are referring to by looking them up on DNS lookup and IP address lookup sites, such as are at
http://whois.domaintools.com/ and many other such facilities. You can experiment to see which ones you like.....
EDIT: Regarding the use of the "hosts" file to filter out known bad web sites by IP address:
I use the hosts file which is provided by the MVPS organization at
http://www.mvps.org/winhelp2002/hosts.htm
Explanations of what that file is, how it works, how to use it, etc. are at the site. The file can be edited to add additional IP addresses.
A similar hosts file is provided by Spybot S&D, a top anti spyware/adware site. You might find these lists more or less credible and easy to use than the Dr. program you are currently using - I am unfamiliar with that one.