I have a picture of my dog and the rest of the house is in the background. I am going to use the pic for a T-shirt and want to erase everything around him.
Select the dog and create a layer mask to hide the rest. Edit the mask to make adjustments as needed.
There are many ways to select in Photoshop: Selection tools in the tools panel, features in the Select menu, Quick Mask, Pen tool, etc. Some are easy, some have a learning curve. Start with Select menu > Select Subject and see how far that gets you. You might start here, then look for other tutorials on selecting.
After you have your selection, click the Layer Mask button at the bottom of the Layers panel to hide the parts you don't want. This is non-destructive editing. Then use the Brush tool "B" with either Black or White to paint directly on the mask to correct the areas that you need to fine tune.
Do not remove or delete the background as one user suggested, as that is destructive editing and you will not be able to clean up your mistakes.
If you are new to Photoshop, then you will want to learn the basics first. Start with Photoshop Essentials by Julieanne Kost on LinkedIn Learning. You can get a free trial before subscribing.
you have to select background with magic select tool, then simple remove it !
Select the Background Eraser tool from the Photoshop toolbox. It may be hidden beneath the Eraser tool. If it is, simply click and hold the Eraser tool to reveal it. Alternatively, you can press Shift + E to cycle through all the eraser tools to get to the Background Eraser.
[Two weblinks in extremely small type removed by moderator.]
If the dog is the main subject of the image, use the Select>Subject and then refine the selection.
Under the Menu System on top Select>Subject. If it is not there, then you are using an older version of PSD and will have to use one of the other methods mentioned.