This explains the differences between Suica and Pasmo, which are very similar.
Basically, they are both transport IC cards.

1．Suica

Suica is issued by East Japan Railway (JR East), Tokyo Monorail and Tokyo Waterfront Area Rapid Transit,
and is used mainly in the Tokyo metropolitan area, but also throughout Japan.

It can be used almost anywhere within the JR East area, making it particularly convenient for regular JR users.

Suica has a smartphone application, Mobile Suica.
Mobile Suica can be used on JR East lines and on sections and routes that involve the use of lines (e.g. Shinkansen).

2. PASMO

PASMO is issued by PASMO Corporation and is sold by 27 railway operators and 78 bus operators in the Kanto region, Yamanashi Prefecture and eastern Shizuoka Prefecture.
This also is a transport IC card issued in partnership with private railway companies.

Like Suica, it can be used at private railway stations and buses in the Tokyo metropolitan area and throughout the country.

Outside PASMO-compatible areas, use is limited, e.g. on the Shinkansen bullet train.
Cash deposits cannot be made at some ticket vending machines, etc.
It cannot purchase green tickets at Suica green ticket vending machines, and
cannot be stacked with an EX reservation-only IC card to pass through Shinkansen transfer gates.

Caution：As of September 2024, continued to suspend sales of no -name “Suica” and “PASMO” cards due to a high likelihood of insufficient stock at the latest available supply volume.

Enjoy your wonderful trip to Japan(^^