ISP is short for Internet Service Provider, which is a company that provides a connection to the internet.
ISP's, like all companies, vary in the quality of their services; those that advertise heavily in the media, are often renowned for the worst reliability and customer service, so be sure to check independant surveys before being locked in to a long contract.
BT, Plusnet, Talk Talk & UW,are all examples of ISPs
Most connections to the internet are via an ADSL broadband signal provided by an ISP, that runs over the old 'landline' telelphone network owned by OpenReach*. A router, often enabled with WiFi, converts the ADSL signal on the phone line into a form that the computer uses to connect to the internet.
With an internet connection being almost as important as a telephone, it is very important to ensure that the connection is as reliable as possible. If a business is predominantly 'cloud' based, it can be looked upon as necessary to have multiple methods of connecting to the internet (e.g. Fibre, ADSL, 3G, Satellite) in case of any failure.
Mobile users can use a wide variety of devices in order to communicate with the work colleagues. It may be by using a laptop, tablet or smartphone. In doing so, is this device secure when it connects via 3G /4G? Is there data stored on it that could be compromised if the device is stolen ? Is it secure from Malware when it connects to the company network via WiFi ? All these questions should have been addressed before the device is used by the user.
Mobile devices require additional security considerations, such as: