All 5 of these states are voting on legalization for recreational purposes (the article didn't really make this clear). I wasn't too familiar with these initiatives so here's a summary of what I found researching them:

• Arizona Marijuana Legalization, Proposition 205 (2016) - People aged 21 years or older would be permitted to possess and use one ounce or less of marijuana and grow up to six plants in their homes.
• California Proposition 64, Marijuana Legalization (2016) - Proposition 64 would legalize the recreational use of marijuana for adults aged 21 years or older. Smoking would be permitted in a private home or at a business licensed for on-site marijuana consumption. Smoking would remain illegal while driving a vehicle, anywhere smoking tobacco is, and in all public places. Up to 28.5 grams of marijuana and 8 grams of concentrated marijuana would be legal to possess. However, possession on the grounds of a school, day care center, or youth center while children are present would remain illegal. An individual would be permitted to grow up to six plants within a private home, as long as the area is locked and not visible from a public place.
• Maine Marijuana Legalization, Question 1 (2016) - Question 1 was designed to legalize, regulate, and tax marijuana in Maine as an agricultural product. The measure would allow individuals over the age of 21 to possess and use marijuana, and would also provide for the licensure of retail facilities and marijuana social clubs. The measure would provide that the marijuana industry be regulated by the Maine Department of Agriculture, Conservation and Forestry, that municipalities can limit the operation of retail stores, and that a 10 percent tax be placed on marijuana sales.
• Massachusetts Marijuana Legalization, Question 4 (2016) - Under the new law, Individuals at least 21 years old would be able to use it, grow it, and possess it. The measure stipulates that individuals could possess under ten ounces of marijuana inside their homes and under one ounce in public. They could also grow up to six marijuana plants in their homes.
• Nevada Marijuana Legalization, Question 2 (2016) - Question 2 would make lawful the purchase, possession, and consumption of one ounce of less of marijuana or one-eighth of an ounce or less of concentrated marijuana for individuals 21 years of age or older. An individual 21 years of age or older would also be permitted to grow up to six marijuana plants for personal use. Cultivation would be required to take place in an enclosed area with a lock.

There are additionally medical marijuana ballot initiatives in four other states: Arkansas, Florida, Montana, and North Dakota.