"RateLimitingException"?!

I suppose it was just a matter of time before my lack of computer know-how would catch up with me...I just got the following message as I tried to post a picture:
"Error: com.google.blogger.exceptions.RateLimitingException: For anti-spam verification purposes, please login to Blogger.com and create a post on your blog. You will need to solve a CAPTCHA."
Does that mean I have posted too many pictures?
What is a Captcha and why should I solve it?
Is that like Russian for a crossword puzzle or something?! ha!ha!