Mental reading (Subvocalization): sounding out each word internally, as reading to yourself. This is the slowest form of reading.
Auditory reading: hearing out the read words. This is a faster process.
Visual reading: understanding the meaning of the word, rather than sounding or hearing. This is the fastest process.
Mental readers generally read at approximately 250 words per minute. Auditory readers read at approximately 450 words per minute. Visual readers read at approximately 700 words per minute.