Both Theravada and Mahayana are Buddhism. They all agree the 4 Buddhist dharma seals as following:
All compounded things are impermanent
All emotions are painful
All phenomena are without inherent existence. They are without inherent existence.
Nirvana is beyond description
Since all phenomena are without inherent existence, the nature of all phenomena are emptiness. Once we can realize the emptiness, then we will get rid the endless suffering of Samsara. But there are differences between both schools in how each school recognizes emptiness and the final objective.
For Theravada school, the final object is to attain Arahant. Arahant can realize the absence of “Self”, can recognize the emptiness of ego, no inherent existence of “I”, but still has attachment to dharmas. The main emphasis in Theravada school is self liberation.
Theravada school is popular in countries like: Sri Lanka, Thailand, Burma, Laos and Cambodia and parts of Southeast Asia.
For Mahayana school, the final objects is to attain Buddhahood via bodhisattva path. A Buddha can recognize both the emptiness of all phenomena. Therefore, Buddha has no attachment to both “ego” and “dharma”. Besides self liberation, it is important for Mahayana practioners to help all sentient beings.
Mahayana school is most practiced in countries like: China, Tibet, Taiwan, Japan, Korea, Mongolia and parts of Southeast Asia.