A meadow is a area of perennial grassland maintained by an annual cycle of growing a hay crop, mowing, and grazing. Grasses and perennial flowers grow and are allowed to set their seeds before being cut for hay. The hay making takes place in late summer. Traditionally, the meadow would then be grazed until the winter, before being shut up again the spring to allow the grass to grow.
Over time, removing the hay reduces the fertility of the soil which allows the flowers to better compete against the more vigorous grasses.
Distinctive species of flowing plants establish themselves. Species such as ox-eye daisy, meadow cranesbill, cowslips, buttercups, red clover and common spotted orchids might be expected. This photo shows a species-rich hay meadow.
The flowers in a hay meadow are not the same as those associated with cornfields which are cultivated each year. In that case the flowers which can grow are annuals such as poppies, cornflowers and corn marigolds.
This website explains the difference.