Infants progress from supporting themselves on their forearms and creeping on their tummies, then move into the crawling position and learn to crawl on different surfaces, up slopes and steps and over obstacles.
Most infants will happily lie on their tummies and quickly learn to push on their arms, lift up their heads and view the works from a different vantage point. Many infants on the other hand hate being on their tummies on a horizontal surface and may need quite a bit of encouragement to get them happy in this position.
Creating many opportunities for your infant to explore crawling on different surfaces as well as up over and under objects helps to strengthen muscles and train coordination and develop curiosity.
