What would you call the thing on this image:
I am looking for the general term, I know that it has more types:
Cereal and grain are the go-to names for these; in Britain, they sometimes use corn. Since your picture shows plants growing on a field, you may choose to be more precise by calling them cereal plants, cereal crops or grain plants/crops.
From a botanical perspective, these plants are all Poaceae (or Gramineae) in taxonomic terminology, and grasses or true grasses in English.