log("normal level of message, visible only via console");
Initial it is an alias to log.info. Could be overridden by
    log.log = log.xxx
where xxx is one of log.levels

The common log severity level could be set by AMD configuration by query "log!logLevel=xxx" shim or directly by setting
    log.severityLevel = log.levels[xxx]

log.error("application malfunction, perhaps worth to log back on server");
[ http://en.wikipedia.org/wiki/Syslog syslog severity levels]