When you take a Log Backup the space in the Log File can then be reused (slight over simplification, but in general "most" of the space will be immediately available for reuse)
A Log Backup can be used to restore to point-in-time - so if you have a Full backup at midnight, all the log backups after that, and you have a disaster at, say, 10:03 then if your last Log Backup was 10:00 then you can restore to 10:00 and only lose 3 minutes changes.
Furthermore, if you have a database corruption, or a hardware failure, it is often possible to take a "tail log backup". So at 10:03 you (successfully) manage to take a Tail Log Backup and in that case you will be able to restore the Full backup from midnight, all the Log Backups up to 10:00 and then you final, Tail Log Backup, and you will lose no data at all.
You should set the interval between log backups according to how much data you can afford to lose, and how big your Log File is growing. 10-minutes is a common interval, so starting with that might be a good compromise. More frequent Log Backups means you will have more backup files (i.e. in a 24 hours period). However, apart from a little overhead the total size, of all the backups, will be the same. So there is very little reason not to take frequent log backups.
For disaster recovery purposes you should also consider what happens if you have a total failure of your server - including any backup files on local disks. So, in addition to copying to tape (e.g. daily) I recommend that you copy all backup files onto A.N.Other server / storage device, perferably off-site if you can, so that in the event of a disaster you have additional copies of all the files both on the original server, and on A.N.Other server.
One other point to note: Log Backups and Full Backups are done using different methods. As such, if your Database becomes corrupted (e.g. disk corruption, disk controller failure/error etc., there there is a very good chance that your Log Backups will NOT also be corrupted. So you can take a final, tail, log backup, restore the most recent "known good" Full backup, and then ALL the Log Backups since then, including your final Tail Backup, and by that means there is a very good chance that the corruption, present in the original database, will no longer be present (in the restored, clean, database)
It is best practice to perform a Database Consistency Check regularly (say, once a week) as that will give you early warning if a corruption is detected in your database. If that finds a corruption, at some future date!, then you can restore from Full and Log backups to fix the problem.