Bodmas tells you what order you do a mathmatical operation in if you had a question like:
Brakets first. So now what? look at it. Divide is above add do 6/2=3 and 3+4=7. now you need to do the last operation which is multiply. 7*3=21. Easy!
What is BIDMAS?
BIDMAS and BODMAS are the same thing. The only difference is it says Indices instead of Order. They are still the same thing it's just a synonym. (Different word, same meaning.)
In school you may get taught either one of these.