It’s not the most fully featured photo app, but Photos is great for the basics

1 Left-hand toolbar

Choose from Adjust, Filter and Straighten modes here. A yellow dot tells you which mode you’re in.

2 Cancel button

Pressing the cancel button discards all the changes you’ve made and returns you to before you pressed the Edit button.

3 Dot dot dot

The threedots button drops down an Options menu, which holds the Markup option, but you can add custom Actions.

4 Right-hand tools

The meat of the app -choose from any of the options and the dial at the far right changes their intensity.