Pastures can be used for grazing and cropping, with the mode being automatically determined by the state of the pasture.
For example, if you are rotating animals in and out year round, it's a grazed pasture, if you put it in crop it will become a cropping or mixed use pasture.
Each pasture contains the following fields:
Name: is a friendly name for the pasture.
Area: is the size of the pasture, refer to your farm settings for the area unit type (Acre / Hectare). Area is used to determine carrying capacity, and stocking rate so if you're exercising rotational grazing, this is a good one to set.
Status: allows you to enable / disable pastures for use.