This is a question I get asked a lot. There are many things that can happen when changing your theme and you can learn more about that in this video post. But in reality, we are mostly concerned with content. If you have 25 pages and 999 blog posts on your site, the thought of them evaporating is downright horrifying.
So let me give you a bit of reassurance.
When you click on All Pages and you see everything you created there. That isn’t going anywhere.
When you click on All Posts, same thing.
That content will remain there when you switch out themes.
It may not show up in your navigation menus, but it’s still there. You just need to either recreate those menus or find out where they went.
It may disappear from your homepage if your theme had certain features that pulled in content. But again, those posts and pages still live on. It’s just a matter of taking that content that didn’t go anywhere and presenting it in a new way using your new themes features. That’s all.
Some themes have post types where you could lose it. Let me give you example.
Let’s say you are using a theme XXX. You have created some content in their custom footer area. You also used the plugin XXX, which is specific for that theme. When you change your theme, that content goes away with the theme. So if you are planning on using any content that you have placed directly into a theme setting, or a plugin that you will also be removing, copy the content and save it.
Another example would be a slider. Some sliders that are built into themes will pull in text content from posts or pages you have created. But if you are using a slider where you have to put the content directly into a slider post, that is part of your theme, and that will disappear with the theme as well.
Lastly, page and site builders all work differently. Of course you are going to lose you layout when moving from one of these. But since a lot of them use shortcodes and have their own special content areas, depending on what you are doing, that content may not be saved once you change themes. Since there are so many on the market these days, before doing any change, or even better, before using one, contact pre-sales and find out what can happen if you need to ever change your theme
So to sum it up. All your regular pages and posts will keep their place in your dashboard. But any content that is set in any feature of your theme, could very likely disappear.
Just give it a bit of thought and exploration before you switch themes and delete that old one.
If in doubt about your theme, research and ask.