AdWords Image Ads
I just creating image ads for an account I have, I found 2 options for ads : HTML5 and Flash. So my question is what is the difference between them and which is more favorable for use?
There are basically different type of ads based on the format being used.
Here you can find the technical difference and requirements which have to be met when you create either HTML 5 ads or Flash ads : https://support.google.com/adwordspolicy/answer/176108?hl=en
Welcome to the AdWords community :-)
Flash isn't supported by all devices, but according to this article AdWords can convert Flash ads into HTML 5 (however there may be a slight variation on how the ad looks)
Check out this article for more information: Create image ads in different sizes
You will find all of the information about the use of Flash and it being converted to HTML 5 under the collapsible heading "Using Flash in your ad?"