SUICA/PASMO/ICOCA prepaid cards
SUICA, PASMO and ICOCA are 3 prepaid cards to use easily any subway or rail line in Tokyo area (Suica e Pasmo) and Osaka/Kyoto area (Icoca) without having to buy each time the ticket. It is much more comfortable than it looks, especially if you use lines of different companies and then you should buy more than one ticket.
These cards do not offer any discount on tickets, their use is tied exclusively to expedite entry into the subway/railway.
SUICA and PASMO cards
The SUICA card can be used with all JR lines in Kanto region (the region of Tokyo), in all lines of the tokyo subway network, both Tokyo Metro and Toei metro, but also with the yurikamome to Odaiba, with the Keisei private railways (for example to Narita), Tobu railways (for example to Nikko), Tozan railways (for example to Hakone), Keio and Odakyu railways, with the subway network of Yokohama, Chiba, Saitama, and many other railway lines. I think I'm not wrong if I say that you can use the SUICA with all railway lines in Kanto region, or anyway if some no-SUICA line exists you will never need to take it if you are a turist.
This card can be used also for all city buses in Tokyo and intercity buses of JR Kanto bus company.
You can use the SUICA also in other regions of Japan (Osaka, Hiroshima, Nagoya, Fukuoka, Sapporo) but only for JR lines
you can use the SUICA in other regions of Japan but only for local lines of each other region.
Example: you can use the SUICA for a JR line inside Osaka city, or from Osaka to a nearby town, but not on Osaka-Tokyo or Osaka-Nagoya trains.
PASMO card and differences
The PASMO card can be used in all lines compatible with the SUICA card but only in the Kanto region. Basically the only difference is that the SUICA can be used also with JR lines of Osaka, Nagoya, etc.
So SUICA and PASMO are the same, you can choose what you want.
Where to buy them
Generally, in each station where SUICA/PASMO can be used there are vending machines to buy them. Therefore for example in all JR stations of Kanto region SUICA can be bought, in all metro stations in Tokyo you can buy both the PASMO and SUICA, etc. The vending machines are usually also in English.
The SUICA can also be bought at Narita airport (very good is the Suica & N'ex
You can choose to to the anonymous card or the nominal one inserting your personal data. The only difference is that with the nominal one, in case of loss you can recover the amount that was loaded in the card.
How much they cost
As regards the SUICA, you have to pay 2000 yen when you buy the card, 1500 yen of which are immediately available to be used as credit, while 500 yen will be refunded when you decide to return the card (at any JR office).
As regards the PASMO, it is almost the same, but if you want to return it you have to go to a Tokyo Metro office.
The ICOCA card is the same, in Kansai
region (Osaka, Kyoto, Kobe), of the SUICA card of Kanto region (Tokyo).
It can be used in almost all railway lines in Kansai, including subways and buses in Osaka, Kyoto, Kobe (I am quoting only the most important cities).
Similar to SUICA, this card can be used in other regions of Japan (Hiroshima, Fukuoka, Tokyo, Nagoya, etc) but only for the JR lines.
Where to buy it
At any enabled machine that you can find inside JR stations of Kansai region, Osaka subway stations, Kyoto stations and others. Generally the vending machines are also in english.
You can choose to buy the nominal card, including your personal details, or the anonymous card. Just as for SUICA/PASMO, the difference is that with the nominal one in case of loss you can recover the amount that was loaded in the card.
How much it costs
It costs the same of SUICA: 2000 yen, 1500 yen of which will be charged as usable credit and 500 yen will be refunded if you decide to return it at a JR office.
How to use them
After you get one of these cards, you can recharge it at the same automatic machines where you bought it, simply inserting it and selecting the desired amount of charge.
To use it, just pass the card near the magnetic reader, but don't insert into the slot for standard tickets.
When you arrive at your destination you have to pass it again in the magnetic reader and the amount of the route will be deducted from the card.
You can check the remaining credit inserting it in the automatic machines (the same used to recharge) or in a small display when you pass the card on the pay gate.
Other prepaid cards
In addition to the SUICA/PASMO and ICOCA cards in Kanto and Kansai regions, other regions of Japan have their prepaid cards and they all work the same way. For example in Nagoya there is the TOICA card, in Fukuoka the SUGOKA, in Sapporo the SAPICA.
Recently, the use of these cards has been extended to other contexts, they can be used as a real pre-paid cards to pay for some things as conbini (convenience stores), vending machines, coin lockers, taxi, or even some stores.
If this is possible you surely notice the logo of the card printed somewhere.