Terminal strips are used anywhere wires need to be joined together. They allow a fixed connection that is readily visible and accessible for troubleshooting. Where there are a lot of wires they organize connections into a logical arrangement.
These Blue Sea Systems Terminal Blocks come in three basic sizes. The smallest is the 20 Amp model. It is really quite tiny and is normally used for electronics, especially data connections and NMEA interfacing. The largest is the 65 Amp model which can be used for Shore Power wiring, wired to heavy duty pumps and motors and can accommodate up to 6 awg wires. The intermediate size is the 30 Amp model and these get used literally everywhere there are wires to be joined together. See my Blog Post for a few suggestions.
The difference between a terminal block and a busbar is that in the terminal block all the connections are separate from each other but on a busbar they are all connected together. Having said that it is possible to use terminal jumpers to connect some of the terminals of a terminal block together.