There are two distinct types of Limited companies: limited by shares and limited by guarantee.
The former is when there are shares and shareholders and profits can be kept. Limited by guarantee has guarantors & invests profits back into the company. This is typically in not for profit companies.
A private limited company (LTD) is also different to a public limited company (PLC). A PLC must have a minimum share capital of £50,000, at least two shareholders, two directors, and a qualified company secretary. Therefore, most small to medium businesses will opt for a private limited company.
A LTD company structure creates a distinct border between the business owner and the business itself, and under the eye of law, the business becomes a separate legal entity in its own right, becoming responsible for its own actions and finances. This in turn limits the liability of the owner from any risk the business may need to take. So if you are a small business expanding & possibly needing employees & assets, then a limited company is a good idea.