Petunia x Hybrida 'Frost' or 'Picotee' is a Petunia cultivar with white rimmed flowers, available in a variety of colours. It is classed as Grandiflora (large flowered), and flowers throughout the summer.
From Wikipedia (http://en.wikipedia.org/wiki/Petunia):
Petunia is a widely-cultivated genus of flowering plants of South American origin, closely related with tobacco, cape gooseberries, tomatoes, deadly nightshades, potatoes and chili peppers; in the family Solanaceae. The popular flower derived its name from French, which took the word petun, meaning "tobacco," from a Tupi-Guarani language. Most of the varieties seen in gardens are hybrids (Petunia × hybrida).