Simple Mail Transfer Protocol governs the transmission of electronic mail through the internet. The programs or applications that perform tasks on your computer are called software. This includes DOS and Windows as well as games. Your SLIP or PPP account is where you dial into for access to the net. In HTML all formatting is done with tags.
Most tags come in pairs, one to open the formatting and one to close it.
A few tags work alone. Software is periodically upgraded by the manufacturer. To differentiate between the different upgrades the manufacturer attaches a different version number.