Joint venture is the partnership between two or more people.
Joint venture can be done in offline and online businesses. E.g. (offline) If i have a car and i want to sell this car, i can get a partner who sells fuel, to partnership with. OR now that xmas is coming closer, i sell electronics and for me to compensate my customers for patronising me, i will simply go into partnership with a poultry seller, food stuff seller,or cosmetic seller who is willing to sell to my customers at a discounted rate and also compensate me for every sells he made through me. If the merchant agreeds, there is nothing to loose, because after xmas he will still get more customers through me and he won't have to compensate me again. He will keep on selling for them weeks after weeks, there is nothing to lose 50-50.
2) E.g. (online) For online jv to take place, the two parties must be selling different products or services. If i have a website that deals on laptops sells, i can look for a jv who offers services like repairs, or internet services or parts like case,hardware,software e.t.c.

NOTE: For a successful jv to occur, the two parties must come to agreement.
And also if you want to engage in any jv partnership, make sure you stand a chance to some certain advantages like earn per refferal, free shopping, exchange of customers and so on.
Regards.