This is the 4134th most frequent Russian word.
ржд
"РЖД" stands for "Russian Railways," the state-owned railway company in Russia.
In this sentence, 'РЖД' refers to 'Российские железные дороги', the Russian Railways state company.
Сегодня мы поедем на поезде компании РЖД в другой город.
Today we will travel by a train of the RZD company to another city.
Here, 'РЖД' identifies the organization responsible for railway operations in Russia.
РЖД предоставляет услуги пассажирских и грузовых перевозок.
RZD provides passenger and freight transportation services.
In this case, 'РЖД' denotes the company as an entity known to the public.