SQL Log file

I'm new to Idera, however the IT group are running SQL Diagnostic tools to help look for a speed issue with a SQL database across a new network.

I have noticed the "live" database LOG file is very large - over 50GB (the mdf file is around 60GB) - when I questioned this I was told this is normal for the log file to grow while the diagnostics tools are running and it is not a concern.

Can anyone explain this to me?  why would the tools would need to (I presume) write to the LOG file.