DPI stands for "dots per inch" and refers to the number of ink droplets a printer will produce per inch while printing an image. DPI is used to describe the clarity and detail of an image on paper, and it is an important measurement for photographers and designers, as it will determine the quality of a printed asset – whether for a poster, a brochure, or a glossy magazine. The higher the DPI, the more ink droplets are tightly bunched together, making the image look crisp and high-quality.

In Photoshop, DPI is used interchangeably with PPI, which stands for "pixels per inch" and refers to the number of pixels in an image per inch. Both acronyms are used to describe the clarity of a picture, but its important to understand that DPI is used for physical photos while PPI is the term for digital files.

To check the DPI of an image in Photoshop, you can go to the "Image Size" option under the "Image" menu. The number in the "Resolution" box is the DPI of the photo. To change the DPI of an image in Photoshop, you can go to the "Image Size" option and change the resolution to the desired DPI. Its important to note that when resampling or interpolating upwards, there can be a loss of detail and sharpness, so its best to work in incremental steps to upsize and try to create an image at a sufficiently high resolution from the start.