You can find the release notes at this link: https://docs.microsoft.com/en-us/business-applications-release-notes/april19/
Some highlights are:
Sales forecasting – with the help of Cortana
Deeper integration with LinkedIn
Teams integration with Relationship Assistant
App licensing requirements presented to app makers while building PowerApps – know if your app will work with your licensing!
Canvas apps with responsive layouts
Save and reuse PowerApps components
