You need about eight tools
Photoshop ships with hundreds of tools, and almost every beginner tutorial tries to tour all of them. That is the slow path. In practice a working editor spends most of the day in a handful: Move, Crop, Lasso, Brush, Clone Stamp, Healing Brush, Curves and Layer Masks. Learn those and you can edit a real photograph.
Learn in this order
Skills in Photoshop stack, so order matters more than volume:
- Layers first. Nothing else makes sense until layers do. Start with how layers actually work.
- Then masks. Masks are how you apply an edit to part of an image without cutting anything. See layer masks explained.
- Then Curves. One dialog covering brightness, contrast and colour. See Curves explained.
- Then selections. Once masks make sense, selections are just a faster way to build one.
- Then retouching. Healing, cloning and frequency separation.
Set the document up correctly
Two settings cause most beginner grief. Work in 8-bit only when you must — 16-bit gives you far more room before tonal edits start banding. And keep the document in sRGB if the image is destined for the web, because a wide-gamut profile like ProPhoto will look flat and desaturated in browsers that ignore it.
The habit that matters most
Edit non-destructively. Never paint on the original pixels, never flatten early, and never use Image → Adjustments when the same tool exists as an adjustment layer. This one habit is what separates an edit you can revise from one you have to redo — see Smart Objects and non-destructive editing.
What "Photoshop online" actually means
Adobe offers a browser version of Photoshop with a reduced tool set, and there are independent web editors like Photopea that mirror the classic interface closely. The techniques on this site are about the ideas — masks, curves, blend modes — and those transfer to any of them, because they are how raster editing works rather than features of one product.