Here is an introductory, straighforward, no-nonsense guide to the words used when discussing satellite TV equipment and reception.
A satellite receiving dish "looks" towards the satellite and collects or focuses the signals on to the LNB. A dish can be "fixed" and look at a single satellite or small group of satellites. A dish can be "motorised" so that it can point to a wider range of satellites. Bigger dishes can receive weaker signals.
A Low Noise Block is attached to the satellite dish assembly. It picks up the satellite signal that is focused on to it by the dish. The LNB is connected by a co-axial cable to the satellite receiver.
Some LNB assemblies have more than one LNB built-in. This is so that each LNB "looks" at a different satellite. The satellite receiver switches automatically between the different LNB's (and satellites) when you change channel. The changeover is immediate; unlike motorized systems, there is no delay. However, the satellites need to be in roughly the same direction, for example the Astra-19.2E and the Hotbird-13E groups of satellites are only a few degrees apart.
FTA TV channels are transmitted without encryption ("in the clear"). They can be received by any suitable equipment and you don't need to pay a subscription to view them. FTA channels are available in many different languages but not all digital TV channels are transmitted FTA.
The STB is the receiver itself. The signal from the dish LNB is carried by co-axial cable to the STB. The STB may receive only FTA channels or may be able to decode encrypted channels and have a slot for a subscription card. The output from the STB is fed to the TV or to a VHS video recorder or DVD recorder. The connection is usually by HDMI (High-Definition Multimedia Interface) or older SCART cable.
Some other satellite TV signals are encrypted so that you cannot receive them without paying a subscription and having a viewing card. There are several different incompatible systems. If you want to use a particular viewing card as well as receiving free channels, you need to check on this before purchasing an STB or subscription card to make sure that your digital receiver is compatible.