A hazelnut is a fruit with a hard case holding a single fruit. An apple is a false fruit. The pips are seeds. If plants are to spread from one place to another, seeds must be scattered or dispersed. Different seeds are dispersed in different ways.
Some seeds are light enough to be blown away.
The feathery seed cases of many grasses can be borne on the wind for several kilometres. Some seeds, such as coconuts, are carried by water. Coconuts can float thousands of kilometres across the ocean before being washed up upon the shore. Many fruits and seeds are dispersed by insects, birds and other animals - either because the animal eats the fruit or because the seed clings to the animal's body. Some fruits simply burst, showering seeds in all directions.