Can someone please explain the polling until condition is met in Rxjs 6 with example

import { timer, from } from 'rxjs' import { map, concatMap, filter, take } from 'rxjs/operators' timer(0, 500) .pipe(concatMap(() => from(fetch(/tasks/${taskId})) .pipe(map(response => response.json()))) ) .pipe(filter(backendData => backendData.processing === false)) .pipe(take(1))