what is the difference between "Norton AntiVirus" and "Symantec antivirus"?
Are they same or different softwares?
Which one is better?
When compared to Microsoft Security Essentials, which one would you recommend? and why?
Norton *anything is usually their home/personal brand so Norton Antivirus would be for personal usage at home. Symantec is usually their corporate branding. So Symantec Antivirus (Corporate Edition) SAVC would be their server based product for business.
Corporate type antivirus solutions are usually server based - the server pushes updates to the clients and monitors who is protected, who isn't, who has updated, who hasn't, who is soing risky stuff...
For home use there will alawys be flame wars as to who is "better." Currently MSE appears to be a relatively light weight (doesn't bog your system down) and decent solution. One of the reasons people hate Norton was that it SEVERELY slowed your system down though recent versions have been better. They were also known for going into your system and sometimes crashing and then refusing to uninstall - you had to really dig it out with special uninstall tools. Again recently they've been better. Note that MSE is changing - their new versions are coming out and they will include more features. How this will affect, no one really knows. Also note that they are free if you have a machine certified as genuine, otherwise they will turn off.
Symantec is the company, Norton is the brand (I guess).
Maybe you are comparing on different sites, different names but same product.
Anyway, my personal and professional choice is ALWAYS
@Blackbeagle answer is correct but here's a simplified version:
Symantec = Company
Microsoft Security Essentials (MSE) = Free antivirus from Microsoft
The difference between Norton and Symantec Antivirus today is in how the definitions are sent out. Norton Antiviurs gets its lists directly from Symantec (company) while Symantec Antiviurs is usually managed by a business's internal IT department.
Historically, Symantec used to also be a lot more resource friendly than Norton which was very resource intensive. Recently, with Norton Antivirus 2010 and 2011, its resource usage is significantly better, and user experience wise, the difference probably only lies with the user interface.
Edit: It should be noted that while Norton and Symantec Antivirus are not free (unless you include deals), an antivirus solution is usually provided by universities if you're student or faculty.