Visiting Japan means using trains, and if you are visiting Japan or living there, it really really helps to get a train pass. If you are traveling across many prefectures or the countryside, then it makes sense to get a JR train pass, however, if you are staying within the inner-city Tokyo area, then you might better off getting a Suica card instead.
Suica cards are extremely useful for getting around town, and also for making purchases at vending machines and convenience stores. They’re easy to setup, easy to reload, and they have no expiration. This important because I travel to Japan with the family yearly, and it’s nice to be able to reload my Suica card as soon as I get there and resume traveling.
JR provides a pretty handy video how to get and use a Suica card:
The video, I think, is filmed at Narita airport (where most international travel happens), because I recognize much of the background scenery. I can attest that once you get to the airport, go to the basement where the trains are, the Suica terminals are right there. The terminals are available in English and other languages, so they’re pretty easy to use too.
Also, as the video points out, transferring between train lines operated by different companies is pretty seamless.
When you want to use your Suica to pay for train fare, you simply go to the appropriate ticket gates, and tape the little scanner:
When you tap at your starting point, it will activate the card, and when you get to your destination and tap the card again, it will deduct the difference. Trains fares are based on distance from one station to another, so they vary.
Also, note that for children, the fare is half of what adults pay, but you can’t get a Suica card like above. You have to go to a JR office and present ID (e.g. a passport) for the child to get one.
Anyhow, I have had my Suica card for maybe 10+ years, and it’s always very handy. I highly recommend getting one no matter you go in Japan, though in western Japan, you might see the equivalent Pasmo more often. They both work great, and will work just about everywhere. It mainly comes down to preference.
Good luck and happy traveling!