Post modules and image modules
The important difference between post slider and image slider modules, is that post slider or post carousel modules draw in the content from blog posts or pages. But with the slideshow and content slider modules you choose the images and text by hand, for each individual slide.
Just remember, if the module has the word post in it, it automatically draws in post content. If the word post is not in the module name, you have to type the content and choose any images or icons yourself.
The Posts Carousel
The Posts Carousel displays the featured image, post title, author's name and post date. You can show some of the post content too if you wish.
The Post Slider
This is a Post Slider. It's easily confused with the content slider.