WHAT IS SHARIA?
Shariah is referred to the sacred Islamic Law. Muslims believe that Shariah is the law of Allah Almighty.
It teaches what are the "do's and don'ts" in Islam and what is lawful for a Muslim and what is not.
In simply, the Shariah is an outer law concerned with actions.
WHAT IS MADHAB?
Madhab are the schools of Islamic Jurisprudence (Fiqh) which are the opinions of great scholars of Islam based on Al Quran and Al Hadith. It is impossible for an illiterate to obtain the laws from Al Quran and Al Hadith for the critical issues or any new issues based on Islamic jurisprudence. He, since, does not possess that knowledge to do so. Thus, the Madhab are the explanations and laws written by the great scholars of Islam to resolve those issues.
There are four Madhab followed by Muslims worldwide. Those are:
Schools of Jurisprudence Founder
Hanafi school Imam Abu Hanifah (May Allah be pleased with him)
Maliki school Imam Malik (May Allah be pleased with him)
Shafi`i school Imam al-Shafi`i (May Allah be pleased with him)
Hanbali school Imam Hanbal (May Allah be pleased with him)
WHICH MADHAB DO I WANT TO FOLLOW?
There is no compulsory in following a particular madhab. It is a personal choice of a person to follow any of these Madhab. Generally, Muslims prefer to follow the madhab which is largely followed in their region. For example, the people who live in North India, Pakistan, Egypt and some part of Arab world follow Hanafi Madhab. While Shafi'i madhab is followed in South India, Sri Lanka, Yemen, Palestine, Syria, Malaysia and Indonesia. Maliki Madhab is followed in North Africa, West Africa, UAE and Kuwait. Hanbali madhab is followed in Saudi Arabia, Qatar and some communities in Syria and Iraq.
Hence, there is no compulsory in following a particular mathhab. But if a person decides to follow a particular madhhab, he should restrict to follow it alone. He should not change it time to time as he wants as he plays. Once he selected, he should start to learn the teachings (Islamic laws/Fiqh) of that madhhab.