I can only speak about the UK and what is probably the equivalents. LLC (Limited Liability Company) and Ltd (actually known as a "private limited company" in the UK) are approximately the same thing. While Ltd may be the format in the UK, LLC is probably the approximate US equivalent. In the case of the LLC or Ltd company, there will be shares issued but these shares would be privately held and traded privately. Inc (Incorporated) or the UK equivalent, PLC (Public Limited Company) are usually much larger organizations whose shares are publically available for trade. There will be different statutory requirements on these different types of companies, with more regulations applying to the INC or PLC. It is extremely unlikely a small company would be a PLC.
there is a big difference between P.LTD and LTD while a private limited company has or can have only 4 members in board of directors one M.D and one sleeping director the LTD needs 22 with a M.D and 2 sleeping directors . also a pvt.ltd cannot make public share offers it needs to be a LTD to do that. INC is a group of companies which all have different public holdings for shares but has one chief board of directors a very good idea when dealing in market funds . i guess different countries will have different company laws and broadly this covers.
In the US an incorporated company could either be an C-corp or an S-Corp. A C-corp is what most larger corporations use and they pay taxes through the corporation itself. An S-corp has a flow through system where the principals of the company pay the taxes for the corporation. The S-corp is more typical for small business. Many small businesses tend to be Self Employed or considered a Sole Proprietorship. The S-Corp is technically a C-corp that elected to work as a S-corp and I think it was designed to bridge the gap between the larger corporations and the smaller mom and pop shops. The LLC came as simple type of corporation to bridge the gap even more. The LLC is much quicker to set up and a lot less expensive than an S-Corp. I've been told that they are best for asset holding companies. I do not know much about the Limited Liability but you should really check with an accountant and an attorney to find out what suits your business the best. Either way if you set up a corporation you need to treat it as a corporation and not just an extension of your personal accounts. If you do not, a court can still look past the corporation and all the protection that you set it up for is worthless. Maybe some others will have more knowledge than me on this.
About.com has an excellent page to describe the differences: http://biztaxlaw.about.com/od/businessorganizationforms/a/legalbizforms.htm
I'm not a lawyer, but it seems while the LLC is easier,as pointed out in the last post, you have less protections than an S corp...
this would be useful http://en.wikipedia.org/wiki/Limited_liability_company and http://en.wikipedia.org/wiki/Types_of_business_entity
For a table comparing a limited liability company, a C corporation and an S corporation under US laws see: http://www.limitedliabilitycompanycenter.com/llc_vs_corp.html