Resolution - also known as DPI (Dots per Inch) or PPI (Pixels per Inch). number of dots that fit horizontally and vertically into a one-inch space.
Generally, the more dots per inch, the more details captured and the sharper the resulting image.
SCREEN DPI vs PRINT DPI
DOWNLOADING IMAGE FROM INTERNET
How to choose the right resolution image file from the internet for your artwork?
If you are searching on the internet for an image to be place is a 2 inch x 4 inch space of your artwork. You will need to find an image size of at least 600 x 1200 dpi.
(Note: 2 inch x 300 dpi = 600 dpi)