You get infected with malware because it modifies your system’s configuration in order to automatically launch and persist the malware’s process.

If the malware is run under the limited account, it will inherit the account’s limited permissions. Since limited accounts cannot modify critical system files, the malware in turn cannot modify these files.

You should be safe from system-wide infection. If the malware is only a "nuisance" program (changes your desktop, icons, or something "annoying" instead of destructive), it will affect the limited account only.

You should create a limited account for your everyday computing regardless. You should only need administrator privileges when doing system or software maintenance. This is just good practice, security-wise.