Hi Jane, I was an IELTS Examiner once upon a time and I can tell you that the topics are very general. Everyone should be able to talk about them without any very specialized knowledge. Of course you should know what words such as 'environment', 'pollution', and 'global warming' mean.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
You could check out ieltspass.com they offer free courses to introduce you to what's included in the ielts and they also have quite cheap courses compared to other resources out there! Good luck