1. Also known as junk mail or unsolicited bulk email, is a subset of electronic spam involving nearly identical messages sent to multiple recipients by e-mail.

1. PPI (pixels per inch) refers to display resolution, or, how many individual pixels are displayed in one inch of a digital image.

2. DPI (dots per inch) refers to printer resolution, or, the number of dots of ink on a printed image.

3. The physical size of an image refers to the dimensions in which it will print (ex: 8.5" x 11") or the pixel dimensions of an image displayed on the web (ex: 600 pixels x 800 pixels).

1. Blind carbon copy is the extended form of BCC used in e-mail communication.

2. It is used to send a copy of an email to a person without informing the recipient about it i.e. the identity of the recipient mentioned in the 'Bcc field' is hidden from other recipients receiving the same email.

3. Recipients in the BCC list can see every other email address, including the To and CC lists.