In a primary emulsion, the globules (droplets) inside emulsion consist of only one substance or phase. That is droplets of oil inside water or water droplets inside oil are primary emulsion.
In a secondary emulsion, the globules inside emulsion consist of two phases. Each droplet consists of a globule encapsulated with in another globule. For example, there is an oil drop on which there is water drop surrounding it, and this droplet is immersed in oil.
Secondary globules and emulsion is formed from the primary emulsion.