Layers and masks.
Stack photos, text and shapes on layers with 16 blend modes, groups and clipping masks, hide parts of a layer with a mask you can paint, and add layer effects: shadow, stroke, glow, bevel, inner shadow and gradient overlay.
Adjustments.
Exposure, contrast, color, curves and levels, a color mixer, black and white and Looks, all on adjustment layers you can change again.
Selections.
Box, ellipse, lasso, magic wand, quick select and color range, with feather, Refine edge for hair, channels and saved selections, so changes land only where you want them.
Retouching.
Heal, clone, spot heal, patch, red-eye, dodge and burn, and content-aware fill to remove what shouldn’t be there. Liquify, warp, perspective and perspective crop to reshape and straighten.
Filters.
Blur, motion and lens blur, tilt-shift, sharpen, noise and pixelate, as smart filters you can tune or turn off later, plus lens correction by hand.
Text, shapes and gradients.
Paragraph text in any Google font with shadow, stroke and glow, rounded shapes and pen-tool paths that stay sharp, gradients, the paint bucket, and a brush library with drawing-tablet pressure.