Zòngzi (粽子) are kind of traditional Chinese food. They come in different shapes and flavors but by principal are all made of glutinous rice, stuffed with different fillings, and wrapped in bamboo leaves. They can be either sweet (usually in Northern China, stuffed with sweet bean paste or chestnuts) or salty (with duck egg, pork or chicken). The greater consumption of zongzi is usually associated with Dragon Boat Festival when people eat ridiculous amount of this food. That doesn’t matter however that you can’t eat zongzi during other time of the year. Actually it’s quite popular form of breakfast or fast-food sold by street vendors (usually near bus or railway stations).
How does it taste? Well that depends on the filling so there’s no one answer to the question. Personally I recommend rather the salty ones (with egg or meat). They make really nice alternative for fast food. They are tasty, stuffing and quite cheap (4-7 RMB, depending on the size, filling and city).