Resolution is a measure of how detailed an image is. The resolution of a digital sensor is measured by the number of pixels it contains. The more pixels the sensor has, the more detailed the image will be. Film doesn't use pixels—the resolution is measured in "angular resolution". If we compare film with a digital sensor, it has an equivalent resolution range of 4 to 16 megapixels, depending on the film type.
However, film photographers are not limited to 35mm format. They can use medium or large format cameras, which have much larger film sizes and higher resolutions. Medium format film can reach an equivalent resolution of 400 megapixels, and large format film can go even higher. Digital cameras cannot match this level of resolution, even with the best sensors available.