There are currently ~300,000 known species of flowering plant, growing in almost every terrestrial environment. The flowering plants have existed on the planet since more than 65 million years ago, but it was about this time they began their current rise to dominance. For the most part, it is only in the colder forests of Earth, in the mountains and the far northern regions, are they outcompeted by the non-flowering plants.
Almost all of the fruits and vegetables which humans depend on for sustenance are flowering plants. The agricultural grains, in particular, are members of the grasses, which are more recently evolved.
From Wikipedia:The flowering plants (angiosperms), also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies (derived characteristics). These characteristics include flowers, endosperm within the seeds, and the production of fruits that contain the seeds.
The ancestors of flowering plants diverged from gymnosperms around 245_202 million years ago, and the first flowering plants known to exist are from 140 million years ago. They diversified enormously during the Lower Cretaceous and became widespread around 100 million years ago, but replaced conifers as the dominant trees only around 60_100 million years ago.
The characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species. The function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds.