With Dynamic forms, you can add field sections in lightning record pages and move fields as a separate component using Lightning App Builder. This feature is in a Non-GA Preview stage and it works for custom objects only. Each field is treated as a component in the lightning builder and similar to the components we can set component visibility rules for each field so that they are shown only when the criteria become true. The visibility rules specify if to show or hide the field.

A good use case for using dynamic forms can be to show only relevant fields and field sections based on the data and hide blank fields if there is no data in them. This can reduce the creation of multiple page layouts and also if you have fewer fields in your page it can reduce page performance and load times.

To enable Dynamic forms in your org, search under Quick Find and go-to Record Page Settings which is under User Interface. Under Dynamic Forms section switch ON the toggle. Once this is enabled you need to open the lightning record page in Lightning App Builder. You need to upgrade the Record detail page for the object which can be found under the Record detail panel. On clicking Upgrade Now it will launch a wizard that will guide you step by step to add fields and field section to your page using just clicks.

For here, you can migrate your lightning record pages to dynamic forms or create new pages by dragging fields and sections into the page

Along with Dynamic Forms, we also get Dynamic Actions which helps in controlling the visibility of actions on the records in your highlight panel. Instead of having multiple actions on your record, we can specify only the ones which are relevant to the record. 

To enable Dynamic Actions, you need to open the Lightning App Builder and open any custom lightning record pages. Click the highlight panel and check the Enable Dynamic Actions. Also, you need to enable Dynamic Forms as well.  Once enabled it removes all the actions from the page builder. You can add actions and specify the visibility criteria for the action you add on the page. This visibility criteria will decide when the action will be displayed.

                                   

A good use case for Dynamic Actions will be to display only the required actions on the page instead of having all the actions on the highlight panel. The visibility criteria can be also set based on the user's permission set. If the user doesn't hold a permission set the action will be visible for the user.

To summarize both Dynamic Forms and Actions they are a great upgrade to the lightning record pages and page layouts. Dynamic Forms and Dynamic Actions work hand in hand and also helps us to provide a single model instead of managing both lightning record pages and page layouts you can just use lightning record pages with Dynamic Forms and Actions enabled.