A limited number of preferred stock issues pay their dividends on a monthly basis instead of on a quarterly basis.
In general there is nothing special with these issues, but “a bird in hand is worth 2 in the bush” and we would rather have the money in our pocket than in the issuers pocket, thus receiving a dividend every month accomplishes our needs. Technically speaking preferred stocks paying monthly dividends yield a bit more over the course of a year than those paying quarterly dividends–but it is not worth worrying about this tiny differential.
Personally, as an investor, I like the dividends that hit my account on a monthly basis. It is just a regular paycheck each month and I like a nice steady flow–but that is just me.
While these particular preferred stocks pay monthly dividends there is nothing else that is different from all other preferred stocks that pay quarterly.