It means there is one week's time between 2 events. The 2 events are separated by 1 week. "Once a week" means the same thing: "On time every 7 days". "Once every other week" means "On time every 2 weeks (14 days)".

Mr. Wright is always right!

Good to see you back on line Mr Wright

I understand now. Thank you Mister Wright! You are a big help.