Partnerships are hard to describe, because they change so much. They are governed by state laws, but a Uniform Partnership Act that has become the law in most states. That act, however, mostly sets the specific partnership agreement as the real legal core of the partnership, so the legal details can vary widely.
Usually the income or loss from partnerships pass through to the partners without any partnership tax. The agreements can define different levels of risk, which is why you’ll read about some partnerships that have general partners and limited partners, with different levels of risk for each. The agreement should also define what happens if a partner withdraws, buy and sell arrangements for partners, and liquidation arrangements if that becomes necessary.
If you think a partnership might work for your business, make sure you do this right. Find an attorney with experience in partnerships, and check for references of present and past clients. This is a complicated area and a mistake in the agreement will cause a lot of problems.
For more on business partnerships, check out Creating a Partnership Agreement, How to Choose a Business Partner, and 6 Traits to Look for When Choosing a Business Partner.