A joint venture (J.V.) is created by two or more parties, who agree to contribute equity (money or stock etc.) to the venture and share in its control, income, and expenditure.
Common reasons to enter into a J.V. are to: increase capacity, enter new markets and develop new products etc. You are most likely to be successful if you share common goals, agree on your investments and trust each other.
A solid agreement is essential! I would say that a J.V. has more potential for unresolved differences than a Company, or maybe a Limited Liability Partnership (LLP), because they have more formal and well established legal structures. Differences in a Company can be settled by shareholders voting, and it is similar in a LLP.
If you want to go ahead with a J.V. make sure you get good advice.