Maintenance plan for creating transaction log backups
You might want to read up on the concept of Transaction Log Backups in the following Microsoft Technet Article: SQL Server - Understanding SQL Server Backups

If you set up a maintenance plan that creates a transaction log backup of all your user databases, then the backup job will create a *.TRN (default extension) file for each database and for each scheduled run.

Depending on the retention period you set in your maintenance plan, you will/can have literally thousands of transaction log backup files (*.trn) in your backup location. 

E.g. Backing up a 10 user databases every 15 minutes and leaving the retention period for clean-up to 30 days, will leave you with 28'800 transaction log backup files lying around.

10 db * 1 trn/db/15min * 1440 min/d * 30d = 28'800 trn files

db = database
trn = trn backup file
min = minutes
d = day


So depending on the size of the databases and the amount of changing data, you could end up needing quite a lot of disk space for your transcation log backups. Then again, having a short retention period in your maintenance plan could result in lower disk space requirements.

Pssst, after reading the Microsoft article, have a look at some alternative backup solutions, like Ola's Maintenance script or other alternative solutions.