Refers to a person at the introductory level of a skill, subject, or activity. Often used in educational or training contexts.
This class is for beginners.
It's software that even beginners can use easily.
初級者 specifically marks someone at the elementary skill level in structured learning like language or music classes, whereas ビギナー is a more general, casual term.
Compound of 初級 (beginner level) + 者 (person).