Modern English
Modern English (sometimes New English or NE as opposed to Middle English and Old English) is the form of the English language spoken since the Great Vowel Shift in England, which began in the late 14th century and was completed in roughly 1550.
Middle English
With the discontinuation of the Late West Saxon standard used for the writing of Old English in the period prior to the Norman Conquest, Middle English came to be written in a wide variety of scribal forms, reflecting different regional dialects and orthographic conventions. Later in the Middle English period, however, and particularly with the development of the Chancery Standard in the 15th century, orthography became relatively standardised in a form based on the East Midlands-influenced speech of London. Spelling at the time was mostly quite regular (there was a fairly consistent correspondence between letters and sounds). The irregularity of present-day English orthography is largely due to pronunciation changes that have taken place over the Early Modern English and Modern English eras.