Power BI free and Pro licenses are different based on the kind of content users can consume. If your content contains any of the following items, it's Power BI Pro content:
Data from a dataset that refreshes more frequently than daily.
Data from a live connection to Azure Analysis Services.
Data (including reports, dashboards or tiles) from a dataset that uses Row-level security (RLS).
A dashboard or report that's installed from an organizational content pack.
A dashboard, report, or dataset that's contained in a group workspace.
A dashboard that contains data streamed at a rate above 10k rows/hour.
Conversely, if your content contains only the following items it will be consumable by both Power BI free and Pro users:
A dashboard or report connected to content packs for services (e.g. Dynamics CRM, Salesforce, and Google Analytics).
A dashboard or report with data imported from files such as Excel spreadsheets, Power BI Desktop, and CSV.
Tiles pinned from a report in SQL Server Reporting Services.
For example, if you create a manufacturing dashboard that updates progress multiple times during the day, anyone consuming that dashboard would need a Power BI Pro license. Or, if you create a report using the Power BI Gateway - Enterprise, then another that uses the personal gateway, anyone consuming or interacting with either of those reports would need a Power BI Pro license.
If you want to share your Power BI Pro content with users, they can sign up for a free trial of Power BI Pro, and gain access to your content during the trial period.
For a list of Power BI Pro features (and how those features compare to a free Power BI license), take a look at Power BI Pricing.