Me not some oracle DBA but u can say me an aspiring DBA

I have this query in my mind rite from the day i started working as a novice DBA in my firm

The d/b in my org is in non archive log mode...

Which 1 is better ...archve or non archive log mode?

If my d.b is runnin on archive i necessarily need to take the backups of all the archive logs ..?

Can any 1 pls explain me this in brief ..the funda behind this...
Thanx a lot