Terrorism: goals and intentions.”* Islamic: This term

Terrorism: Terrorism does not have a definition that all Member States has reached a consensus upon. However, in a general sense it can be defined as an act of violence intended to create fear and terror in people and society. The conditions that pave the way for terrorism does not have to be religiously driven. 
Islamist terrorism: claims to be inspired by Islam. Islamist terrorism or Radical Islamist terrorism is generally defined as “any terrorist act, set of acts or campaign committed by groups or individuals who professor Islamist motivations or goals. Islamist terrorists justify their violent tactics through the interpretation of Quran and Hadith according to their own goals and intentions.”*
Islamic: This term should not be used with the world terrorism, as it is found offensive by the administrations of countries which have a large number of Muslims in their society, such as Turkey, Malaysia and Indonesia.  It associates Islam in general as a religion with terrorism. Islamic is an adjective to define Muslims and the religion Islam and it refers to the 1.6 billion Muslim population all over the world whereas Islamist is a twentieth century construct that has a political entity to itself and is destructive for people all over the world, including Muslims (So, the correct term to refer to the terror acts or personas is Islamist or Islamist terrorism not Islamic terrorism.)
Islamism: The term was originally used to describe the religion Islam, with having no political aspect to it. After the Islamic Revolution of 1978-79, the term gained a political aspect. With the establishment of new Islamist Government the term became an ideology just like fundamentalist Islam, radical Islam and literalist Islam. After the 9/11 accidents, Islamism was  no longer used to describe the religion Islam but rather was used to describe the ideology which interpreted Quran literally and had the aim of imposing any version of Islam over society. It is the political manifestation (formally or informally) of Islam. It differentiates from Islam as Islam is the religion followed by Muslims without having a political entity whereas Islamism is an ideology that with or without violence tries to enforce their message and terrorise populations into submission. Overall, Islamism includes a variety of Islamist movements and does not represent Muslims or Islam. 
Sheria: With being unconstitutional in many countries, Sheria is laws and legislations of Islam that are regarding the socio-economic, political and cultural aspect of adherents and their code of living. It is inspired by Holy Book Quran, Prophet Mohammed and hadiths.