Pretty simple @lina. Images and Containers are the same, barring one difference.
Think of it this way, Images are inert (inactive) volumes containing everything your application needs to run. Containers however are the active version of images which actually hosts your application.
Images and Containers work like Car and Fuel.
Without their compatriot/ partner, they are useless. And when they are working together, we are happy for what is being produced.
In other words, Images are the templates with all the data about the app. When the image is executed, a Container is created which actually contains that app.
For a better understanding of how this works, watch this video of mine. I've explained it as clearly as possible with diagrams, demo, etc: https://www.youtube.com/watch?v=h0NCZbHjIpY