If two or more of you set up in business together you automatically form a partnership. In order to form a Limited Liability Partnership (LLP) you need to register the LLP with Companies House. Similarly to set up a limited company you need to register with Companies House. Ralli can help you do either of these things.
There are pros and cons to each form of business. The main difference between a partnership and a company is that a partnership does not have a separate legal personality; that is the partnership does not exist as a separate entity in law, whereas a limited company does exist in law. The other main difference is that a limited company, as the name implies, has limited liability; if the company ceases to trade the owners and directors are not directly liable for any losses unless there has been fraudulent activity or other wrongdoing.
A limited company is taxed as a company and its directors are employees who can be paid either a salary, which is taxable or can take out dividends if they are also shareholders, which can be more tax effective. The individual partners in a partnership are taxed individually on their share of the profit of the partnership. The partners do not have to declare their income or turnover openly unlike in a limited company.
A Limited Liability Partnership (LLP) is a half way house. The LLP has legal personality, i.e. it exists and can form contracts; it needs to disclose accounts at Companies House, but the members, like partners, are still taxed as individuals.
Certain professions, such as Lawyers and Accountants have historically had to act as partnerships or LLPs. In most situations if you are not a professional and you are looking to trade then a limited company is the most sensible way of going forward.