The amount you pay each month including taxes. This does not include extra costs such as eg. a telephone line, modem rental, ... unless stated otherwise.
For most ADSL line types you are required to have an active phone line with a telecom provider. Some providers cover this for you either free or for a fee.
A fixed IP allows you to easily run a server. If you do not have a fixed IP then it will change every X hours and/or when you reconnect your connection.
Webmail allows you to read your mail on the website of your provider. This can be usefull to read your mail while not at home, e.g. at work or on holiday.